# Client Research: Model-facing MCP Resource & SEP-2640 Support > **Scope.** This page tracks two related areas of client support: > > 1. **Model-facing MCP resource loading** — does the client expose a tool that lets the model trigger an MCP `resources/read`? This is the SHOULD proposed in [modelcontextprotocol/modelcontextprotocol#2527](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/2527) (which phrases it as "by URI"); for survey purposes we also count by-name variants where the framework resolves a model-supplied name to a URI before calling `resources/read` (adk-python is the one such case found). The bulk of this page is this survey. > 2. **SEP-2640 skills extension support** — as clients ship [SEP-2640](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/2640) implementations, this page tracks them. **fast-agent is the first surveyed client to ship one** (registry/install scope — see its deep dive), verified live against the Hugging Face MCP server, which is the first server-side implementation we've interoperated with. SEP-2640-related issues, PRs, and shipped implementations are tracked per-client in the "Open issues/PRs to watch" column rather than via a separate status field. > > ℹ️ **SEP-2640 claims here are pinned to a draft revision.** The July 8–15, 2026 v1 rework ([2026-07-16 decision record](decisions.md)) removed archives, replaced `skill://index.json` with a `skills/list` method, replaced the single per-entry digest with a per-file `resources` manifest, added `skills/get`, and gated `resources/directory/read` behind a `directoryRead` capability. **fast-agent has since realigned to that shape** — its docs pin draft revision [`d7490ec`](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/2640/commits/d7490ecd1a250f7bc8c3ebb0d65450dfec274bad) and explicitly drop the older index/archive path — as has its server counterpart, both confirmed by [@evalstate](https://github.com/evalstate) in Discord (2026-08-04). Note the client side ships behind a prerelease install (`--prerelease=allow`; see its deep dive). This is the second realignment (the first was 2026-06-19); since the SEP is still a draft under review, expect further churn and re-verify against the SEP's current revision. The SEP is now at [`0eb05fe`](https://github.com/modelcontextprotocol/modelcontextprotocol/blob/0eb05fe9fbd6b4c5e3fbe7e097028dd0b68a10cf/seps/2640-skills-extension.md) (2026-08-05), but that delta leaves the wire contract intact, so `d7490ec` pins remain compatible — see [skills-extension-candidates.md](skills-extension-candidates.md) for what it does change. > > **Why these are tracked together.** SEP-2640 layers skills on top of MCP resources. If a host's progressive-disclosure flow involves the model itself loading L2/L3 skill content from `skill://…` or related resource URIs, then the resource-read affordance for the model becomes critical for skills. A client's resource-loading shape today is a strong predictor of how it'll fit SEP-2640 tomorrow. > > See also [**skills-extension-candidates.md**](skills-extension-candidates.md) for the matching server-side tracker: MCP servers, dev tools, SDKs, and skills repositories that are candidates for adopting SEP-2640. > ## At-a-glance comparison Category values: **Framework** = SDK/library you build agents on top of · **CLI** = end-user coding agent or CLI · **IDE** = editor-embedded chat surface. | Client | Category | Tool exposed to model? | Tool name(s) | Tool signature | Calls `resources/read` on connected server? | Enablement gate | End-user docs? | Open issues/PRs to watch | | :--- | :--- | :--- | :--- | :--- | :--- | :--- | :--- | :--- | | **codex** (OpenAI) | CLI | Yes | `read_mcp_resource`, `list_mcp_resources`, `list_mcp_resource_templates` | `(server, uri)` — server explicitly named | Yes — handler calls `session.read_resource()` | Any MCP server is configured (`params.mcp_tools.is_some()`) | No — only the LLM-visible tool description; an internal steer tells the model to prefer `tool_search` | _none yet — add as found_ | | **goose** (Block) | CLI | Yes | `read_resource`, `list_resources` | `(extension_name, uri)` on `read_resource` — `extension_name` required; `list_resources` takes an optional `extension_name` filter | Yes — `ExtensionManager::read_resource` → `client.read_resource(...)` | ≥1 enabled extension reports `ServerCapabilities::resources` | Yes — [`extension-manager-mcp.md`](https://github.com/block/goose/blob/main/documentation/docs/mcp/extension-manager-mcp.md) | _none yet — add as found_ | | **fast-agent** | Framework | Yes (multiplexed) | `get_resource` (no model-facing `list_resources`) | `(uri, server_name=None)` — `server_name` optional; also handles bundled `internal://` URIs through the same tool | Yes for MCP URIs — `_read_resource()` → `agent.get_resource(resource_uri=uri, namespace=server_name)`; `internal://` URIs short-circuit to bundled resources | Opt-in — `config.harness_tools`, default `False` (also stripped when `tool_only`) | Partial — `skills-over-mcp.md` covers the SEP-2640 install flow; the `get_resource` tool itself has no dedicated docs section | **SEP-2640 v1 shipped** (registry/install scope) — consumes the `io.modelcontextprotocol/skills` extension to install skills via `skills/list` / `skills/get` + per-file digest-verified `resources/read` ([`skills_extension.py`](https://github.com/evalstate/fast-agent/blob/main/src/fast_agent/mcp/skills_extension.py), [`mcp_registry.py`](https://github.com/evalstate/fast-agent/blob/main/src/fast_agent/skills/mcp_registry.py), [`skills-over-mcp.md`](https://github.com/evalstate/fast-agent/blob/main/docs/docs/mcp/skills-over-mcp.md)); pins draft `d7490ec` and treats legacy `skill://index.json` `skill-md`/archive entries as unsupported; still does not read skill resources at model runtime. Verified live against [hf-mcp-server](https://github.com/huggingface/hf-mcp-server). **Watch:** [#816](https://github.com/evalstate/fast-agent/pull/816) (still open) adds MCP-served skill *runtime* loading (URI-backed manifests, `SkillReader` resource reads, untrusted-content wrapping) | | **vscode** (GitHub Copilot) | IDE | Yes (FS-provider indirection) | `copilot_readFile`, `copilot_listDirectory` (general-purpose, not MCP-specific) | `(path)` — accepts `mcp-resource://…` URIs as paths; the FS provider routes to MCP RPC | Yes — `mcp-resource://` URIs route via `IFileService` → `McpResourceFilesystem` provider → `r.readResource(...)` MCP RPC ([`mcpResourceFilesystem.ts`](https://github.com/microsoft/vscode/blob/main/src/vs/workbench/contrib/mcp/common/mcpResourceFilesystem.ts)) | Server must advertise `McpCapability.Resources`; model needs a URI to pass (typically obtained from a user attachment — the earlier Copilot Chat `resource_link`→`mcp-resource://` pre-wrap has since been removed; see deep dive) | No explicit doc, but mechanism is operational. [Connor Peet's comment on #2527](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/2527#issuecomment-4282395437) is the clearest write-up | _none yet — add as found_ | | **opencode** | CLI | No | — (internal `readResource` only) | — | Internal only — `readResource()` exists in [`packages/opencode/src/mcp/index.ts`](https://github.com/anomalyco/opencode/blob/main/packages/opencode/src/mcp/index.ts) but is invoked only when the user attaches a resource via file picker; `mcp.tools()` in `prompt.ts` forwards MCP *tools* but never a resource-read tool | n/a | Docs (`mcp-servers.mdx`) advertise tool forwarding only | _none yet — add as found_ | | **deepagents** (LangChain) | Framework | No | — | — | n/a — delegates MCP wiring to [`langchain-mcp-adapters`](https://github.com/langchain-ai/langchain-mcp-adapters) (via `convert_mcp_tool_to_langchain_tool()` / `_build_cached_mcp_tool()` in [`mcp_tools.py`](https://github.com/langchain-ai/deepagents/blob/main/libs/code/deepagents_code/mcp_tools.py)); that adapter only converts MCP tools, not resources | n/a | No mention in README | **Upstream-blocked**: needs a change in `langchain-mcp-adapters` (or a deepagents wrapper around `client.read_resource()`) | | **strands-agents** (AWS) | Framework | No (internal SDK only) | — | — | Internal only — `MCPClient.read_resource_sync()` and `list_resources_sync()` in [`mcp_client.py`](https://github.com/strands-agents/harness-sdk/blob/main/strands-py/src/strands/tools/mcp/mcp_client.py) call MCP `resources/read` / `resources/list`, but `MCPAgentTool` (the only adapter) wraps `mcp.types.Tool` only and `MCPClient.load_tools()` (the `ToolProvider` interface) returns tools only | n/a | No — `docs/MCP_CLIENT_ARCHITECTURE.md` and `AGENTS.md` do not mention MCP resources | _none yet — add as found_ | | **Claude Code** (closed source, reference) | CLI | Yes | `ReadMcpResourceTool` | `(server, uri)` per [public docs](https://code.claude.com/docs/en/tools-reference) | Documented; source not verifiable | n/a | Yes — public tools reference page | n/a | | **adk-python** (Google ADK) | Framework | Yes (by name, not URI) | `load_mcp_resource` | `(resource_names: array[string])` — model passes catalog names; framework resolves each to a URI and calls `session.read_resource(uri=…)`. The catalog is injected into the model's context by `_append_resources_to_llm_request()` rather than via a separate list call | Yes — `McpToolset.read_resource()` calls `session.read_resource(uri=…)` ([`mcp_toolset.py`](https://github.com/google/adk-python/blob/main/src/google/adk/tools/mcp_tool/mcp_toolset.py)) | Opt-in via `use_mcp_resources=True` on `McpToolset` (default `False`) | No — no user-facing docs found | _none yet — add as found_ | | **agent-framework** (Microsoft) | Framework | No (tools-only client bridge) | — | — | n/a — `MCPTool` / `MCPStdioTool` / `MCPStreamableHTTPTool` / `MCPWebsocketTool` in [`_mcp.py`](https://github.com/microsoft/agent-framework/blob/main/python/packages/core/agent_framework/_mcp.py) materialize MCP *tools* into the agent's tool registry; no `read_resource` callsite found in client code (only in a test) | n/a | Samples cover MCP tool integration only | _none yet — add as found_ | | **cline** | IDE | Yes | `access_mcp_resource` | `(server_name, uri)` | Yes — [`McpHub.readResource(serverName, uri)`](https://github.com/cline/cline/blob/main/apps/vscode/src/services/mcp/McpHub.ts) calls `resources/read`; invoked from [`AccessMcpResourceHandler`](https://github.com/cline/cline/blob/main/apps/vscode/src/core/task/tools/handlers/AccessMcpResourceHandler.ts) | Server's `resources` capability surfaces in system prompt context via the [`mcp.ts` formatter](https://github.com/cline/cline/blob/main/apps/vscode/src/core/prompts/system-prompt/components/mcp.ts) | No dedicated user-facing docs found | _none yet — add as found_ | | **crewAI** | Framework | No | — | — | n/a — `crewai-tools` MCP adapter ([`mcp_adapter.py`](https://github.com/crewAIInc/crewAI-tools/blob/main/crewai_tools/adapters/mcp_adapter.py)) is built on `mcpadapt` and converts MCP tools only — same upstream-blocked pattern as smolagents | n/a | MCP adapter docs cover tools only | **Upstream-blocked** by `mcpadapt` (shared with smolagents) | | **hermes-agent** (Nous Research) | CLI | Yes | `mcp_{server}_read_resource`, `mcp_{server}_list_resources` (one pair per connected server) | `(uri)` — server is encoded in the tool name | Yes — `_make_read_resource_handler()` in [`tools/mcp_tool.py`](https://github.com/NousResearch/hermes-agent/blob/main/tools/mcp_tool.py) calls `session.read_resource(uri)` and registers the tool per server | Two gates: `tools.resources` config flag (default on) AND server's advertised `capabilities.resources` | Yes — [`features/mcp.md`](https://github.com/NousResearch/hermes-agent/blob/main/website/docs/user-guide/features/mcp.md) and [`guides/use-mcp-with-hermes.md`](https://github.com/NousResearch/hermes-agent/blob/main/website/docs/guides/use-mcp-with-hermes.md) | _none yet — add as found_ | | **mastra** | Framework | No (internal SDK only) | — | — | Internal only — [`resource.ts`](https://github.com/mastra-ai/mastra/blob/main/packages/mcp/src/client/actions/resource.ts) exposes a `read(uri)` SDK method that calls `client.readResource(uri)`, but it is **not** registered as an LLM-facing tool; the model-facing tool bridge converts MCP tools only | n/a | SDK docs cover the action; no LLM-tool exposure | _none yet — add as found_ | ## Cross-cutting observations 1. **Three implementation patterns for model-facing MCP resource access.** 1. **Dedicated MCP resource tools** — Codex, Goose, Claude Code, Cline: explicit `read_mcp_resource` / `read_resource` / `access_mcp_resource` (+ optional `list_*`) registered alongside other MCP tools. Most discoverable by the model; closest literal reading of #2527. adk-python is a near-relative — its `load_mcp_resource` takes a batch of `resource_names` in one call rather than a single URI, but the affordance shape is the same. 2. **Multiplexed resource tool** — fast-agent: one `get_resource` tool handles both bundled (`internal://`) and MCP URIs behind a single name. Simpler surface for the model; relies on URI scheme to disambiguate. 3. **FS-provider indirection via namespaced URIs** — VS Code: no MCP-specific tool. A dedicated URI scheme (`mcp-resource://`) is registered with the filesystem service so the generic `readFile` / `listDirectory` tools transparently reach MCP `resources/read`. Reuses the agent's existing file-reading affordance; costs nothing in tool-count budget. Downside: no `list` equivalent — the model can only read URIs it's been handed. 2. **Dedicated-tool implementers converge on `(server, uri)`.** Codex, Goose, Claude Code, and Cline all take an explicit *required* server identifier alongside the URI. fast-agent takes the same pair but with `server_name` **optional** — the one surveyed implementation where the model may omit server identity entirely, which is the failure mode the takeaways flag below. hermes-agent is the remaining variant in pattern (1)'s family: it encodes server-in-tool-name (one tool per server) and takes only `(uri)`. adk-python is the outlier — it takes `(resource_names: array[string])` and resolves URIs via a model-visible catalog injected into context. 3. **Trust models diverge.** Per-server enablement (Goose), unconditional-when-MCP-configured (Codex), capability-gated FS provider (VS Code), capability-gated dedicated tool (Cline), or framework opt-in flag (adk-python, `use_mcp_resources=True`, default off). For skills-over-MCP this matters because the "who can read what" boundary is currently set by each host individually — a portable skill that depends on `resources/read` will work or not based on whether the host considers MCP resource access a model-grade affordance. 4. **Discoverability differs sharply between patterns — and within them.** Within pattern (1), discovery shapes diverge: Codex, Goose, hermes-agent (per server), and Claude Code pair `read_*` with a `list_*` tool so the model can enumerate resources on its own; Cline instead injects each server's `resources` and `resourceTemplates` into the system prompt via its `mcp.ts` formatter; adk-python injects an in-context catalog of resource names via `_append_resources_to_llm_request()`. Pattern (2) (fast-agent) has *no* model-facing `list_resources` on current main — of its two harness tools only `get_resource` reads resources; `list_resources` exists on the agent/aggregator but is never registered as a tool. Pattern (3) (VS Code) has *no list equivalent* — the model can only read a URI it's been handed (user attachment → chat context, or an MCP tool returning a `resource_link`). For skills this matters less than it once did: v1 moved enumeration to a `skills/list` *method*, which the host calls directly rather than routing through the model's resource-read tool — so a client's missing `list_resources` no longer blocks skill discovery. It still matters for the L2/L3 step, where the model reads specific skill files by URI. 5. **VS Code's FS-provider pattern is worth its own consideration for skills.** Because `mcp-resource://` URIs are first-class in the file service, *any* tool that takes a path argument in VS Code can transparently read MCP resources — including, in principle, a skill loader. The skills-over-MCP design could lean on this by treating `skill://server/name/SKILL.md` as just another URI scheme registered with the host's file abstraction. This is closer to a registry-style integration (cf. how VS Code surfaces skills via `ChatSessionCustomizationProvider` rather than as system-prompt content). ## Per-client deep dives ### Agent SDKs / frameworks #### fast-agent Verified at commit [`79b903c`](https://github.com/evalstate/fast-agent/commit/79b903c) (0.10.1, 2026-08-04). **Restructured since the prior `10a996b` (2026-06-02) check:** `smart_agent.py` is gone and the `smart` tool with it; the model-facing harness tools now live in [`core/harness_tools.py`](https://github.com/evalstate/fast-agent/blob/main/src/fast_agent/core/harness_tools.py). - **Model-facing tool:** `get_resource`, registered via `agent.add_tool(...)` in `set_harness_tools()` alongside `slash_command` (the two members of `HARNESS_TOOL_NAMES`). `_read_resource()` routes `internal://` to bundled resources; everything else hits the connected MCP server via `agent.get_resource(resource_uri=uri, namespace=server_name)` → MCP `resources/read`. - **Signature:** `(uri, server_name=None)` — multiplexed across bundled and MCP URIs by scheme, and `server_name` is now **optional**, so the model can omit the server identifier (see the server-identity point in the takeaways). - **Enablement changed — now opt-in, default off.** Gated on `agent.config.harness_tools`, which defaults to `False` ([`agent_types.py:115`](https://github.com/evalstate/fast-agent/blob/main/src/fast_agent/agents/agent_types.py)); harness tools are also stripped when `tool_only` is set. This page previously recorded fast-agent as unconditional for every `SmartAgent` — that is no longer accurate, and it moves fast-agent into the same opt-in category as adk-python's `use_mcp_resources=True`. - **No model-facing `list_resources`:** unchanged — `list_resources` exists on the agent/aggregator but is not registered as a tool, so the model can only read a URI it's been handed. **SEP-2640 v1 skills extension (shipped — registry/install scope).** Verified at commit [`79b903c`](https://github.com/evalstate/fast-agent/commit/79b903c). fast-agent is the first surveyed client to ship a SEP-2640 implementation, and has now realigned to the v1 shape. - **Pinned draft revision.** [`skills-over-mcp.md`](https://github.com/evalstate/fast-agent/blob/main/docs/docs/mcp/skills-over-mcp.md) pins compatibility to SEP-2640 revision [`d7490ec`](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/2640/commits/d7490ecd1a250f7bc8c3ebb0d65450dfec274bad) and states plainly that this is "draft compatibility, not support for a ratified MCP standard." Legacy servers publishing `skill://index.json` with `skill-md` or archive artifacts are **explicitly unsupported** — the older path was removed, not kept alongside. Pinning the SEP revision in user-facing docs is a practice worth noting for other implementers. - **What it implements:** the *registry and installation* portion of the SEP, not model-facing resource loading. When a connected server advertises the `io.modelcontextprotocol/skills` extension capability (`server_supports_mcp_skills()` checks `capabilities.extensions` in [`mcp_registry.py`](https://github.com/evalstate/fast-agent/blob/main/src/fast_agent/skills/mcp_registry.py)), fast-agent treats it as an MCP-backed skills registry. - **Flow (v1):** `/skills registry` calls paginated `skills/list`; installing an entry refreshes it via `skills/get`, then fetches every file named in its `resources` manifest through `resources/read` and requires each to match its declared SHA-256 before writing the local copy. Sidecar metadata records host-assigned server identity, skill URI, and the manifest. Entries omitting `resources` (dynamically generated skills) are listed but **not installable** — no complete digest manifest means no integrity check and no update revision. - **Exercises v1's unlisted-skill path.** `/skills add skill://acme/example/SKILL.md` installs a skill absent from the listing, with the server confirming the URI via `skills/get` — the exact gap the [2026-07-15 `skills/get` decision](decisions.md) was written to close, now with a working implementation behind it. Name-collision handling is implemented per v1 too: same-named listing entries are preserved and disambiguated by URI, though the local managed directory still admits only one skill per name. - **Integrity ≠ trust.** The docs carry an explicit warning that a passing SHA-256 check only means the bytes match the manifest *that server supplied* — it does not authenticate server or publisher, nor vouch for the skill's instructions. Useful framing for the [threat model](threat-model.md). - **Provisional wire models.** The pinned MCP Python SDK ships no typed SEP-2640 models, so fast-agent carries its own for `skills/list`, `skills/get`, and `resources/directory/read` ([`skills_extension.py`](https://github.com/evalstate/fast-agent/blob/main/src/fast_agent/mcp/skills_extension.py)). A concrete data point on what adopting the extension costs while SDK support lags. - **Install requires opting into prereleases.** Per [@evalstate](https://github.com/evalstate) (fast-agent's author) in Discord, v1 support must be installed as `uv tool install -U --prerelease=allow fast-agent-mcp` — `fast-agent-mcp` 0.10.1 is published on PyPI, but it pins `fastmcp-slim[server]==4.0.0b1` (plus `mcp==2.0.0` / `mcp-types==2.0.0`), and uv refuses prerelease dependencies unless told otherwise. So the first end-to-end SEP-2640 v1 client stack is reachable only through a prerelease install path — worth knowing before treating "shipped" as "generally available." - **Still not model-facing at runtime.** Active skills do **not** read supporting files from the MCP server during a session; [PR #816](https://github.com/evalstate/fast-agent/pull/816) ("Add MCP-served skill runtime support") remains **open**. The SEP-2640 path is still host-driven install, distinct from the model-facing `get_resource` tool above. (The `SkillReader` in main serves local skill files in non-ACP contexts, not MCP-served ones.) - **Realignment history:** two rounds. [#825](https://github.com/evalstate/fast-agent/pull/825) (merged 2026-06-19, with [#831](https://github.com/evalstate/fast-agent/pull/831) hardening) moved it to the 2026-06-05 contract; the v1 migration landed later inside the 0.10 release series ([#892](https://github.com/evalstate/fast-agent/pull/892)/[#905](https://github.com/evalstate/fast-agent/pull/905)) rather than as a standalone skills PR. - **Verified against a live server:** the [Hugging Face MCP server](https://github.com/huggingface/hf-mcp-server) is the server-side counterpart, which migrated to v1 in [#219](https://github.com/huggingface/hf-mcp-server/pull/219) (merged 2026-08-03); see its row in [skills-extension-candidates.md](skills-extension-candidates.md). fast-agent's docs walk through `/mcp connect --name hf https://huggingface.co/mcp` → `/skills registry hf` → `/skills add`. --- #### adk-python (Google ADK) Verified at commit [`61a3933`](https://github.com/google/adk-python/commit/61a39330d) (2026-06-03). - **MCP integration:** [`src/google/adk/tools/mcp_tool/`](https://github.com/google/adk-python/tree/main/src/google/adk/tools/mcp_tool) package — `McpToolset` (lowercase c; `MCPToolset` is a deprecated alias) is the entry point used by callers to connect an ADK agent to an MCP server. - **Resource RPC wired:** [`mcp_toolset.py`](https://github.com/google/adk-python/blob/main/src/google/adk/tools/mcp_tool/mcp_toolset.py) exposes `async def read_resource(self, name, readonly_context=None)` which calls `session.read_resource(uri=resource_info["uri"])`. - **Model-facing tool:** [`load_mcp_resource_tool.py`](https://github.com/google/adk-python/blob/main/src/google/adk/tools/load_mcp_resource_tool.py) defines `load_mcp_resource`. **Not two-shot** — the tool's input schema is `resource_names: array[string]` (one call returns the contents of N resources). The catalog of available resources is exposed to the model via `_append_resources_to_llm_request()` injecting it into the LLM context, rather than via a separate `list` tool. - **Enablement:** opt-in via the `use_mcp_resources=True` constructor flag on `McpToolset` (default `False`). When set, `get_tools()` appends `LoadMcpResourceTool` to the toolset alongside the dynamically discovered MCP tools. - **End-user docs:** none found in `README.md` or the docs folder — the affordance is undocumented for end users despite being implemented. - **Why interesting:** ADK is the client with the most rigorous skill validation in the parallel skills survey, so this is where the spec extension and the resource-tool extension converge. The batch `resource_names` shape is a distinct fourth signature among dedicated-tool implementers. --- #### agent-framework (Microsoft) Verified at commit [`c3901a4`](https://github.com/microsoft/agent-framework/commit/c3901a4dd) (2026-06-03). - **MCP integration:** Multi-transport client tools — `MCPTool` plus `MCPStdioTool`, `MCPStreamableHTTPTool`, `MCPWebsocketTool` in [`_mcp.py`](https://github.com/microsoft/agent-framework/blob/main/python/packages/core/agent_framework/_mcp.py). The client-facing methods are `load_tools()`, `call_tool()`, `load_prompts()`, `get_prompt()` — no resource methods. .NET equivalents (e.g. `DefaultMcpToolHandler`) under [`dotnet/src/`](https://github.com/microsoft/agent-framework/tree/main/dotnet/src) expose `InvokeToolAsync()` only. - **Resource RPC wired:** No MCP resource RPC at the model boundary. The only production `read_resource` callsites are in [`_skills.py`](https://github.com/microsoft/agent-framework/blob/main/python/packages/core/agent_framework/_skills.py) and refer to **skill** resources, not the model-facing MCP `resources/read`. All MCP `resources/read` references are confined to tests. - **Update:** upstream has since added **MCP-based skills *discovery*** (recent commits use MCP resources internally for skill metadata / `skill://index.json` lookups via `_skills.py`) — but this is still not exposed to the model as a resource-read tool. - **Why on the list:** dual-stack Python/.NET framework with rich skills metadata in the parallel skills survey. The asymmetry — skills support without a model-facing MCP resource tool — is the kind of gap a #2527-aligned PR would close. --- #### crewAI Verified at commit [`051fa0c`](https://github.com/crewAIInc/crewAI/commit/051fa0c1c) (2026-06) of the main `crewAI` repo, which vendors `crewai-tools` under `lib/crewai-tools/` (the adapter is now under `lib/crewai-tools/src/crewai_tools/`). - **MCP integration:** [`mcp_adapter.py`](https://github.com/crewAIInc/crewAI/blob/main/lib/crewai-tools/src/crewai_tools/adapters/mcp_adapter.py) imports `mcp` (`StdioServerParameters`, `CallToolResult`, `TextContent`, `Tool`) and `mcpadapt.core` (`MCPAdapt`, `ToolAdapter`); `CrewAIToolAdapter.adapt(func, mcp_tool: Tool)` converts MCP tools to CrewAI `BaseTool` objects. - **Resource RPC wired:** No — `adapt()` is typed to accept only `mcp_tool: Tool`; zero matches for `resource`/`Resource` anywhere in the adapter file or directory. `_run()` extracts `CallToolResult` content only. - **Model-facing tool:** None. - **Why on the list:** Same upstream block as **smolagents** — both depend on [`mcpadapt`](https://github.com/grll/mcpadapt) (`mcpadapt>=0.1.9` declared as optional dep in `lib/crewai-tools/pyproject.toml`), which is tools-only. A single upstream change in `mcpadapt` flips both clients. This is the highest-leverage adapter-library target identified so far. --- #### deepagents (LangChain) Verified at commit [`436409f`](https://github.com/langchain-ai/deepagents/commit/436409fc) (2026-06-03). Note the repo has since been restructured into a monorepo — the MCP code now lives under `libs/code/deepagents_code/`. - **MCP wiring is outsourced** to `langchain-mcp-adapters` — [`mcp_tools.py`](https://github.com/langchain-ai/deepagents/blob/main/libs/code/deepagents_code/mcp_tools.py) calls `convert_mcp_tool_to_langchain_tool()` / `_build_cached_mcp_tool()` (the older `load_mcp_tools()` entry point is no longer used). The adapter does not expose `resources/read` as a tool — zero hits for resource-read in deepagents source; sessions only call `list_tools()` / `call_tool()`. - **What it would take:** either upstream adds a resource-read tool, or deepagents wraps `client.read_resource()` outside the adapter. --- #### mastra Verified at commit [`f82cc72`](https://github.com/mastra-ai/mastra/commit/f82cc72edc) (2026-06). - **MCP integration:** [`packages/mcp/src/client/client.ts`](https://github.com/mastra-ai/mastra/blob/main/packages/mcp/src/client/client.ts) imports `Client` from `@modelcontextprotocol/sdk/client/index.js`. [`actions/resource.ts`](https://github.com/mastra-ai/mastra/blob/main/packages/mcp/src/client/actions/resource.ts) exposes `public async read(uri: string)` which directly returns `this.client.readResource(uri)`. - **Resource RPC wired:** Yes, but **internal SDK only**. `ResourceClientActions` is mounted as `this.resources` on the client — an SDK surface for callers, not registered as an LLM-facing tool. - **Model-facing tool:** No. The model-facing bridge is `tools()` at [`client.ts`](https://github.com/mastra-ai/mastra/blob/main/packages/mcp/src/client/client.ts) which calls `this.client.listTools()` and iterates only the returned tools array — resources are never traversed. - **Why on the list:** Mastra's skill versioning architecture (content-addressable BlobStore, draft→publish lifecycle) is the most sophisticated. Unlocking resource-read at the model boundary would be a small change relative to the rest of the framework — the SDK plumbing already exists. --- #### strands-agents Verified at commit [`0e0035f`](https://github.com/strands-agents/harness-sdk/commit/0e0035fb) (2026-06). Strands matches the **mastra pattern**: resource RPC wired in the SDK, but no model-facing tool. The Python SDK lives in the `strands-py/` package of the `strands-agents/harness-sdk` monorepo. - **Resource RPC wired but unbridged:** `MCPClient.read_resource_sync()`, `list_resources_sync()`, and `list_resource_templates_sync()` in [`mcp_client.py`](https://github.com/strands-agents/harness-sdk/blob/main/strands-py/src/strands/tools/mcp/mcp_client.py) are SDK-public methods, but [`MCPAgentTool`](https://github.com/strands-agents/harness-sdk/blob/main/strands-py/src/strands/tools/mcp/mcp_agent_tool.py) only wraps `mcp.types.Tool` and delegates to `call_tool_async(...)`. Outside tests, nothing in the repo invokes the resource methods. - **Why on the list:** Strands has its own local-filesystem skills implementation at [`agent_skills.py`](https://github.com/strands-agents/harness-sdk/blob/main/strands-py/src/strands/vended_plugins/skills/agent_skills.py), so the framework already does progressive disclosure. Wiring resource-read to the model is the obvious next step for an MCP-backed skill story. --- ### Coding agents / CLIs #### codex (OpenAI) Verified at commit [`ad2012d`](https://github.com/openai/codex/commit/ad2012d645b7146d31bb03f98e2bd9371635d11a). (The handlers were reorganized from the single `codex-rs/tools/src/mcp_resource_tool.rs` file into a per-tool module directory since the prior `67849d9` check.) - **Model-facing tools:** `read_mcp_resource`, `list_mcp_resources`, `list_mcp_resource_templates`, each a handler module under [`codex-rs/core/src/tools/handlers/mcp_resource/`](https://github.com/openai/codex/tree/main/codex-rs/core/src/tools/handlers/mcp_resource); registered unconditionally via `add_mcp_resource_tools` in [`spec_plan.rs`](https://github.com/openai/codex/blob/main/codex-rs/core/src/tools/spec_plan.rs), gated on `context.mcp_tools.is_some()`. The read handler [`read_mcp_resource.rs`](https://github.com/openai/codex/blob/main/codex-rs/core/src/tools/handlers/mcp_resource/read_mcp_resource.rs) calls `session.read_resource(&server, …)`. - **Signature:** `(server, uri)` — model names the server explicitly. No user-facing doc; an internal steer (in `apps_instructions.rs`) tells the model to prefer `tool_search`. --- #### goose (AAIF) Verified at commit [`45d8bf8`](https://github.com/aaif-goose/goose/commit/45d8bf81d09d478ceedba8f6d1f0ad906123a981). - **Model-facing tools:** `read_resource`, `list_resources` registered in [`ext_manager.rs`](https://github.com/aaif-goose/goose/blob/main/crates/goose/src/agents/platform_extensions/ext_manager.rs) when at least one extension reports `ServerCapabilities::resources`. Dispatch flows through [`extension_manager.rs`](https://github.com/aaif-goose/goose/blob/main/crates/goose/src/agents/extension_manager.rs) → `client.read_resource(...)` → MCP `resources/read`. Documented at [`extension-manager-mcp.md`](https://github.com/block/goose/blob/main/documentation/docs/mcp/extension-manager-mcp.md). - **Signature:** `(extension_name, uri)` on `read_resource` — `extension_name` is required. `list_resources` takes an optional `extension_name` filter; the tool description directs the model to call `list_resources` first when ownership is unknown. --- #### hermes-agent (Nous Research) Verified at commit [`03ba06e`](https://github.com/NousResearch/hermes-agent/commit/03ba06ebf) (2026-06). No drift across the 376 commits since the prior `72ff3e9` check. - **MCP integration:** Full integration in [`tools/mcp_tool.py`](https://github.com/NousResearch/hermes-agent/blob/main/tools/mcp_tool.py). - **Resource RPC wired:** Yes — `_make_read_resource_handler()` calls `await server.session.read_resource(uri)`; the per-server schemas are built in `_build_utility_schemas()`. - **Model-facing tools:** Yes — both `mcp_{safe_name}_read_resource` (taking `uri`) and `mcp_{safe_name}_list_resources` (no parameters) registered per connected server via `_build_utility_schemas()`. Conditionally registered when the server advertises `capabilities.resources` AND the per-server `tools.resources` config flag is on (default). - **Signature:** `(uri)` — server is encoded in the tool name (one tool per server), so the model implicitly selects the server by selecting the tool. **Distinct from every other pattern surveyed**: not `(server, uri)`, not `(resource_names: array[string])` batch, not `(uri)`-with-probing, not URI-virtualized — it's *one tool per server*. The matching `list_resources` per server gives the model a discovery affordance without cross-server probing. - **End-user docs:** [`features/mcp.md`](https://github.com/NousResearch/hermes-agent/blob/main/website/docs/user-guide/features/mcp.md) and [`guides/use-mcp-with-hermes.md`](https://github.com/NousResearch/hermes-agent/blob/main/website/docs/guides/use-mcp-with-hermes.md) both document the utility wrappers. (Minor doc/code mismatch: the user-facing docs name the tools as bare `read_resource` / `list_resources`, but the actual model-facing names include the `mcp_{server}_` prefix.) - **Why interesting:** The per-server-tool naming is a candidate disambiguation pattern for skills-over-MCP — the model can't pick the wrong server because each tool only binds to one. --- #### Claude Code (closed source — reference only) Claude Code is closed source so we cannot verify the loader, but the [public tools reference](https://code.claude.com/docs/en/tools-reference) documents `ReadMcpResourceTool` accepting `server` and `uri` parameters. Listed here as a reference data point for the `(server, uri)` signature shape also adopted by Codex, Goose, fast-agent, and Cline. --- #### opencode Verified at commit [`2a33add`](https://github.com/anomalyco/opencode/commit/2a33addd2) on the canonical `dev` default branch. - **Tools forwarded to the model** in [`packages/opencode/src/mcp/index.ts`](https://github.com/anomalyco/opencode/blob/main/packages/opencode/src/mcp/index.ts) via `client.callTool()`; tool naming convention `{server_name}_{tool_name}` (sanitized, underscore-separated — `sanitize(clientName) + "_" + sanitize(mcpTool.name)`). The model-tool bridge in [`packages/opencode/src/session/tools.ts`](https://github.com/anomalyco/opencode/blob/main/packages/opencode/src/session/tools.ts) forwards only `mcp.tools()`. - **Resource-read is UI-only:** `readResource()` in the same file is invoked only from the file picker (`session/prompt.ts` attachment path), never registered as an LLM tool. Docs ([`mcp-servers.mdx`](https://github.com/anomalyco/opencode/blob/main/packages/web/src/content/docs/mcp-servers.mdx)) advertise tool forwarding only. --- ### IDE extensions #### vscode (GitHub Copilot) Verified at commit [`ebb335f`](https://github.com/microsoft/vscode/commit/ebb335fad02) (vscode core, 2026-06-03); the Copilot Chat extension was re-checked against current `microsoft/vscode-copilot-chat` main. VS Code is the unique pattern here: no MCP-specific tool — generic `copilot_readFile` / `copilot_listDirectory` tools transparently reach MCP servers via filesystem-provider indirection on a custom URI scheme. - **URI scheme + FS provider:** [`McpResourceURI`](https://github.com/microsoft/vscode/blob/main/src/vs/workbench/contrib/mcp/common/mcpTypes.ts) defines `mcp-resource://` URIs that encode the MCP server's definition ID in the authority — self-routing. [`McpResourceFilesystem`](https://github.com/microsoft/vscode/blob/main/src/vs/workbench/contrib/mcp/common/mcpResourceFilesystem.ts) is registered for that scheme; `_readURIInner` decodes the URI, looks up the `McpServer`, and calls `r.readResource(...)` — the MCP `resources/read` RPC. Capability-gated on `McpCapability.Resources`. - **`resource_link` pre-wrap — removed:** the doc previously described `mcpLanguageModelToolContribution.ts` converting an MCP tool's `resource_link` into an `mcp-resource://` URI for later re-reading via `copilot_readFile`. As of current main that file is gone and `microsoft/vscode-copilot-chat` no longer references the `mcp-resource://` scheme at all. The core scheme + FS provider in vscode itself remain intact, but the extension no longer auto-wraps `resource_link`s — so the model now has fewer built-in ways to obtain such a URI (the live forwarding path observed in the local clone renders `resource_link`s as plain text). *Worth re-confirming the current intended mechanism upstream.* - **Caveat — discoverability:** the model can only read a URI it has been handed (e.g. a user attachment). No `list_mcp_resources`-equivalent **for the model**. Note vscode core *does* now expose `IMcpServer.resources()` / `resourceTemplates()` ([`mcpTypes.ts`](https://github.com/microsoft/vscode/blob/main/src/vs/workbench/contrib/mcp/common/mcpTypes.ts)), but these feed a *user-facing* resource quick-pick (`mcpResourceQuickAccess.ts`), not a model tool. [Connor Peet on PR #2527](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/2527#issuecomment-4282395437) is the clearest write-up of this pattern. --- #### cline Verified at commit [`81792d2`](https://github.com/cline/cline/commit/81792d20c) (2026-06-04). Note the repo restructured into a monorepo — the VS Code extension source now lives under `apps/vscode/src/` (was `src/`). - **MCP integration:** Depends on `@modelcontextprotocol/sdk` `^1.25.1` per `apps/vscode/package.json`. - **Resource RPC wired:** Yes. [`McpHub.readResource(serverName, uri)`](https://github.com/cline/cline/blob/main/apps/vscode/src/services/mcp/McpHub.ts) issues a raw `resources/read` request against the named connection's client and decodes with `ReadResourceResultSchema`. - **Model-facing tool:** Yes. [`AccessMcpResourceHandler`](https://github.com/cline/cline/blob/main/apps/vscode/src/core/task/tools/handlers/AccessMcpResourceHandler.ts) calls `mcpHub.readResource(...)` from the model-tool execution pipeline. The model sees `access_mcp_resource` as a registered tool taking `(server_name, uri)`. - **Discoverability:** The [system-prompt formatter](https://github.com/cline/cline/blob/main/apps/vscode/src/core/prompts/system-prompt/components/mcp.ts) enumerates each connected server's `resources` and `resourceTemplates` in `formatMcpServersList()`. Populated by `fetchResourcesList()` and `fetchResourceTemplatesList()` in `McpHub.ts`. - **End-user docs:** none found in `README.md`; no `docs/` directory in the repo root. - **Why interesting:** Cline has the most extensive skills implementation in the parallel survey (incl. the admin-locked enterprise `globalSkills` primitive), so the *presence* of full resource-read support, in-prompt enumeration, and dedicated handler is the natural complement. ## Takeaways for SEP-2640 (skills extension) - **v1's protocol surface has a working client/server pair, and realignment is fast but not free.** fast-agent and hf-mcp-server have both migrated to the July v1 shape (fast-agent pinning revision `d7490ec`; hf-mcp-server via [#219](https://github.com/huggingface/hf-mcp-server/pull/219), 2026-08-03), so `skills/list`, `skills/get`, per-file digest verification, and `directoryRead` gating are all exercised end-to-end — including v1-specific paths like installing an unlisted skill by URI through `skills/get`. Two observations for the WG: (a) this pair has now realigned **twice in seven weeks** (2026-06-19, then early August), and each round was a breaking change — both implementations dropped the old shape rather than supporting both, and fast-agent's archive download/extract hardening was discarded outright when archives became a deferred feature; (b) neither can lean on the SDK — fast-agent carries provisional local wire models because the pinned MCP Python SDK has no typed SEP-2640 models, which is a standing cost for every adopter until the SDKs catch up. Implementation experience is real evidence for the SEP's readiness here, but it is evidence about a pinned revision, so it should be re-dated whenever the draft moves — and about a prerelease install path on the client side, not a generally-available one. - **First shipped client + server pair.** **fast-agent** is the first surveyed client to ship a SEP-2640 implementation — but scoped to *registry/install*: it consumes the `io.modelcontextprotocol/skills` extension to install digest-verified skills into its managed skills directory, and does not (yet) read skill resources at model runtime ([#816](https://github.com/evalstate/fast-agent/pull/816) still open). It was verified live against the **Hugging Face MCP server**, the first server-side implementation we've interoperated with (advertises the extension with `directoryRead: true` plus `resources: { subscribe: false, listChanged: false }`; tracked in [skills-extension-candidates.md](skills-extension-candidates.md)). One deployment detail worth carrying into the SEP discussion: HF serves skills **over HTTP transports only**, not over long-lived STDIO. Notably, the first real-world wrinkle was operational, not protocol-level: a client that retry-loops `resources/subscribe` (cursor-vscode) flooded the HF server, prompting a client-denylist mitigation ([hf-mcp-server#164](https://github.com/huggingface/hf-mcp-server/pull/164)) — a reminder that serving skills as resources inherits the resource subsystem's failure modes. - **Seven of thirteen open-source clients surveyed** (Codex, Goose, fast-agent, VS Code, hermes-agent, adk-python, Cline) satisfy #2527's SHOULD; closed-source Claude Code's public docs confirm it does too. Goose and hermes-agent also satisfy the implicit expectation that this be documented for end users; the other implementers ship the affordance with no user-facing documentation. - **Four implementation patterns** for model-facing MCP resource access — all support the layering Peter sketches in his #2640 comment, but with different costs: - **Dedicated tools, `(server, uri)`** (Codex, Goose, Claude Code, fast-agent, Cline — fast-agent is also multiplexed across `internal://`): explicit `read_resource` / `access_mcp_resource` registered alongside other MCP tools. Most discoverable; closest literal reading of #2527. By volume, this is the dominant pattern. - **Dedicated tool, `(resource_names: array[string])`** (adk-python): batch read; the available resources are surfaced to the model via context injection rather than a separate list tool. Same affordance shape as the `(server, uri)` family but with the server identifier embedded in the catalogued resource name rather than passed as a parameter. - **One tool per server, `(uri)`** (hermes-agent): server is encoded in the tool name (`mcp_{server}_read_resource`), so the model selects the server by selecting the tool. Trades catalog tokens for unambiguity. Pairs with `mcp_{server}_list_resources` so the model has a per-server discovery affordance. - **FS-provider indirection via namespaced URIs** (VS Code): no MCP-specific tool. `mcp-resource://` URIs are registered with the file service; generic `readFile` / `listDirectory` tools transparently reach `resources/read`. Costs nothing in tool-count budget; loses `list` affordance. Reliability implication: each pattern enforces server identity differently — explicit parameter (`(server, uri)`), tool choice (per-server tool), catalog-name lookup (adk-python), or URI authority (`mcp-resource:///...`). **The spec should nudge implementations to keep server identity mandatory** so a skill always resolves to its owning server. Otherwise the host has to probe every connected server when the model omits it — either silently picking the wrong one, or iterating through all of them at the cost of latency and tokens. fast-agent's optional `server_name` is the live instance of this: notably, its SEP-2640 install path does *not* inherit the ambiguity, since `/skills registry ` binds a specific server and skill provenance is recorded per install — a useful signal that skill-scoped operations want stronger server binding than a general resource-read tool. - **Adapter libraries block two "no" rows.** **crewAI** depends on [`mcpadapt`](https://github.com/grll/mcpadapt); **deepagents** depends on [`langchain-mcp-adapters`](https://github.com/langchain-ai/langchain-mcp-adapters). Both adapters are tools-only — the unlock for either client lives in the adapter, not the client repo. - **Internal SDK without LLM-tool exposure** (mastra, strands-agents) is its own pattern: the resource RPC is wired in the SDK but not bridged to the model. Closing this gap is typically smaller-scope than wiring the RPC from scratch.