c1fa4f315e* docs: add skills-extension-candidates tracker Scaffold a candidates list for MCP servers, dev tools, SDKs, and skills repositories that could adopt SEP-2640. Initial entries: FastMCP 3.0 Skills, chrome-devtools-mcp, hf-mcp-server, Hugging Face skills library, github-mcp-server (PR #2428 demo), Azure Skills Plugin. Cross-link from related-work.md and add a row to the README docs table. * docs: add Issue/PR tracker column to candidates table * docs: add client-mcp-support survey alongside candidates tracker * docs: link Azure MCP Server source in candidates table * docs: remove gemini-cli from client MCP support survey * docs: verify hermes-agent, switch source refs to main-branch links, refresh takeaways - Promote hermes-agent from first-pass to verified; note its per-server tool pattern (`mcp_{server}_read_resource` + `mcp_{server}_list_resources`) and confirm end-user docs exist - Drop stale line numbers throughout; convert path refs to GitHub source-file links on `main` (commit-pinned URLs decayed once files moved) - Goose: PR #8989 has landed, so describe current `(extension_name, uri)` required signature and drop the now-closed issue/PR tracking - Takeaways: collapse to three implementation patterns (Goose now fits the `(server, uri)` bucket), fix open-source count to fourteen, drop the smolagents name-drop (not in survey), add strands-agents alongside mastra for the internal-SDK-only pattern, and reframe the signature recommendation around server-resolution reliability rather than URI portability * docs: verify remaining first-pass clients, flip cline/Roo-Code to Yes Verified adk-python, agent-framework, crewAI, mastra, cline, Roo-Code against local source clones. Two corrections to prior state: - cline and Roo-Code both expose access_mcp_resource(server, uri) as a model-facing tool via McpHub.readResource. Flipped from No to Yes. - adk-python's load_mcp_resource takes resource_names: array[string] in a single call (not two-shot); opt-in via use_mcp_resources flag. Headline count updated from six to eight of fourteen open-source clients satisfying #2527. Cross-cutting observations and takeaways adjusted for the new (server, uri) family members and the four-pattern signature breakdown. Trust-model list extended. * docs: add Figma and Adobe MCP as SEP-2640 testing candidates * docs: update FastMCP 3.0 Skills entry with detailed notes on SEP-2640 compliance * docs: drop unconfirmed Cursor SEP-2640 entry, track latest SEP-2640 wire-contract PRs Remove the Cursor row + deep dive (reported WIP never confirmed). Add the in-flight PRs realigning to the 2026-06-05/06-09 SEP-2640 schema (frontmatter + archives[] index, resources/directory/read): hf-mcp-server#174, fast-agent#825, huggingface/skills#172. * docs: add Slack (interested) and Bloomberg (internal use) as SEP-2640 candidates * docs: remove archived Roo-Code from client survey, update strands repo to harness-sdk * docs: re-verify SEP-2640 implementations against current upstream main Both reference implementations have migrated to the July 2026 v1 shape, verified against fresh clones rather than the prior June commit pins: - hf-mcp-server (d794b10, v0.4.6): skills/list + skills/get, per-file {uri,digest} resources manifest, directoryRead:true, no index.json or archives. Migrated in #219 (merged 2026-08-03). Also records the snapshot/TTL model and HTTP-transport-only constraint. - fast-agent (79b903c, 0.10.1): pins SEP-2640 revision d7490ec, treats legacy index.json skill-md/archive entries as unsupported. Requires --prerelease=allow (pins fastmcp-slim 4.0.0b1), per @evalstate. Corrects the earlier note claiming implementations lagged the SEP: the #174/#825/#172 round merged 2026-06-19 and was never in flight, and a second realignment followed the v1 rework. Also fixes drift found while re-checking fast-agent's resource tool: smart_agent.py is gone (now core/harness_tools.py), get_resource is opt-in via harness_tools (default False, was unconditional), and server_name is now optional - the one surveyed client where the model may omit server identity. Runtime skill loading is still unshipped; #816 remains open. 🦉 Generated with [Claude Code](https://claude.com/claude-code) * docs: track SEP revision 0eb05fe and add mcpkit to the candidates tracker The SEP moved from d7490ec to 0eb05fe (2026-08-05). The delta is editorial for the wire contract -- skills/list, skills/get, and the per-file resources manifest are unchanged -- so d7490ec-pinned implementations stay compatible. Records what it does change: a soft reg-name constraint on the first skill-path segment, the skill root URI fixed as skill://<skill-path> with no trailing slash, whether skills/get carries ttlMs/cacheScope reopened, and normative host obligations in the security section. Adds mcpkit (panyam/mcpkit, Go, v0.3.0) from #118 as a candidate. It implements the pre-v1 index.json catalog shape with per-file digests, so the ecosystem is now split across draft revisions rather than uniformly caught up. 🦉 Generated with [Claude Code](https://claude.com/claude-code) * docs: refine mcpkit entry — deliberate tracking, partial v1 migration Checked mcpkit's issues and PRs rather than inferring alignment from code shape. Its lag is a tracked decision, not drift: - #1185 (merged 2026-08-04) implements origin-tagging and per-origin resolve citing SEP L179/L183/L185 -- the host obligations 0eb05fe made normative -- so it is already on v1 for the security section. #1187 adds a SEP-2640 security/conformance harness as a WG demo. - #780 is an explicit index-schema tracking issue that has absorbed the archives removal and the resources:[{uri,digest}] direction but waits on WG confirmation; its conformance fork pins provenance at 556154c. - The carrier change is still unbooked: nothing references skills/list or skills/get. - Archives are kept as a non-spec extended surface rather than deleted, unlike fast-agent -- a counter-case for whether deferring a feature removes it from the ecosystem. Sharpens the callout accordingly: the draft split runs within an implementation, not only between them, so "which draft does X implement" often has no single answer. 🦉 Generated with [Claude Code](https://claude.com/claude-code)
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Related Work
SEPs and Proposals
| Proposal | Venue | Description |
|---|---|---|
| SEP-2640 (Skills Extension) | MCP Spec | This WG's proposed extension: skills served over MCP using the Resources primitive and skill:// URI scheme (v1 baseline text) |
| PR #2527 | MCP Spec | Recommend clients expose resource read to models — prerequisite for the resources-based skills approach |
| skills.json format proposal | MCP Registry | Skills metadata in registry schema |
| MCP Spec | resources/list, per-resource capabilities, resources/metadata endpoint |
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| MCP Spec |
See also skills-extension-candidates.md for a tracker of MCP servers, dev tools, SDKs, and skills repositories that are candidates for adopting the skills extension.
Working Group Member Implementations
Work by WG leads and active participants that directly implements the group's core patterns: SKILL.md with YAML frontmatter, skill:// resource URIs, and progressive disclosure via MCP primitives.
| Implementation | Author | URL | Notes |
|---|---|---|---|
| skilljack-mcp | Ola Hungerford | github.com/olaservo/skilljack-mcp | SKILL.md, skill:// resources, tools, and prompts; progressive disclosure (index→skill→files); file watching for dynamic updates; audience annotations |
| skills-over-mcp | Keith Groves | github.com/keithagroves/skills-over-mcp | SKILL.md, skill:// resources with progressive disclosure (index→skill→documents); Zod validation against Agent Skills spec |
| skillsdotnet | Peder HP | github.com/PederHP/skillsdotnet | C# implementation: SKILL.md, skill:// resources, load_skill tool for progressive disclosure, manifest with file hashes; published on NuGet; compatible with FastMCP 3.0 |
Alternative Approaches
Work by WG members and MCP maintainers that explores skills over MCP through different technical approaches than the core SKILL.md / skill:// pattern.
| Implementation | Author | Organization | URL | Notes |
|---|---|---|---|---|
| skillful-mcp | Kurtis Van Gent | Google Cloud | github.com/kurtisvg/skillful-mcp | Progressive disclosure via 4 lightweight tools (list_skills, use_skill, read_resource, execute_code); wraps downstream MCP servers as skills using mcp.json config rather than SKILL.md; sandboxed code execution via Monty |
| Astronomer agents | Kaxil Naik | Astronomer | github.com/astronomer/agents | Production skills catalog for Apache Airflow (blueprint, migration, warehouse-init); uses SKILL.md frontmatter but distributed via plugin marketplace rather than MCP resources; demonstrates real-world skills adoption at scale |
| mcpGraph skill | Bob Dickinson | TeamSpark.ai | github.com/TeamSparkAI/mcpGraph | Declarative YAML-based tool orchestration engine (directed graphs of MCP tool calls); includes SKILL.md files as documentation; explores a complementary "no-code composition" approach to skill authoring |
Other Community Implementations
External projects building on skills patterns or integrating skills into frameworks.
| Implementation | Author | URL | Notes |
|---|---|---|---|
| FastMCP 3.0 Skills | FastMCP | gofastmcp.com/servers/providers/skills | Native skills provider (#2694) |
| PydanticAI Skills | PydanticAI | pydantic/pydantic-ai#3780 | Agent skills with tools-based approach |
| mcp-execution | bug-ops | github.com/bug-ops/mcp-execution | Compiles MCP servers into skill packages; --dry-run preview |
| mcp-cli | philschmid | github.com/philschmid/mcp-cli | Wraps MCP servers as CLI for progressive disclosure |
| my-cool-proxy | karashiiro | github.com/karashiiro/my-cool-proxy | MCP gateway with skills as resources via Lua scripts; result offloading, session persistence (v1.6.x) |
| NimbleBrain skills repo | NimbleBrain | github.com/NimbleBrainInc/skills | Monorepo with .skill artifact format |
| NimbleBrain registry | NimbleBrain | registry.nimbletools.ai | Registry with skill metadata support |
| NimbleBrain skill:// servers | NimbleBrain | github.com/NimbleBrainInc | skill:// resource colocation examples: mcp-ipinfo, mcp-webfetch, mcp-pdfco, mcp-folk, mcp-brave-search |
| Kiro powers directory | Kiro | github.com/kirodotdev/powers | Plugin directory bundling skills + MCP servers; active catalog (AWS, GCP migration, SAM, etc.) |
| mcpkit (ext/skills) | Sri Panyam | github.com/panyam/mcpkit | Go SDK, server + host: SKILL.md, skill:// resources, progressive disclosure (skill://index.json catalog + host load_skill tool); per-supporting-file digests with verified reads, resource-fetch size + per-server byte budget, resources/directory/read; no code-execution surface (enforced by a build-failing test); released in v0.3.0 |
Related Ecosystem Work
Projects that illustrate the problem space or use adjacent patterns.
| Project | Author | URL | Notes |
|---|---|---|---|
| chrome-devtools-mcp | Google (ChromeDevTools) | github.com/ChromeDevTools/chrome-devtools-mcp | Real-world example of the problem: skills/ folder requires separate install path |
| Strands Agents MCP server | AWS | github.com/strands-agents/mcp-server | Docs-as-MCP: TF-IDF search + doc fetch |
| AWS MCP server | AWS | docs.aws.amazon.com/aws-mcp/… | retrieve_agent_sop (skills) + call_aws (tool) |
Specifications and Standards
- Agent Skills Standard: agentskills.io
- Agent Skills Discovery RFC v0.2.0 (Matt Silverlock / Cloudflare): github.com/cloudflare/agent-skills-discovery-rfc — Domain-level skill discovery using
/.well-known/agent-skills/(RFC 8615). Definesindex.jsonwith progressive disclosure,skill-mdandarchivedistribution types,$schemaversioning, SHA-256 content integrity, and archive safety requirements. Complementary to MCP-level discovery:.well-knownanswers "what skills does this domain publish?" while MCP answers "how does the agent consume them at runtime?" - Skill dependency declaration: agentskills/agentskills#110 — Discusses how skills should declare their tool/server dependencies
- Apache Airflow AIP-91 (MCP integration): cwiki.apache.org/…/AIP-91+-+MCP
Integrity, Content Addressing, and Attestation
Related work on establishing and verifying the integrity, authenticity, and provenance of skill resources.
- skill-set format (draft) (Harry Martin / flocker.md): skill-set.md — Transport-agnostic manifest specification and CLI for named, versioned collections of skills assembled from disparate sources. Defines deterministic whole-skill content hashes and set-level roll-ups, lockfiles, receipt-time content verification, and optional out-of-band URL-fragment pins. Complementary to SEP-2640: provides prior art for deriving a single content address from a complete
{uri, digest}resource set and for future whole-skill or multi-skill attestations. See the reference directory for an immutable example.
Background Reading
- Anthropic's guidance on progressive disclosure: Equipping agents for the real world with agent skills
- "MCP and Skills: Why Not Both?" (Kurtis Van Gent): kvg.dev/posts/20260125-skills-and-mcp/ — Frames MCP (connectivity) and Skills (context saturation) as complementary; discusses hybrid approaches
- "Skills Over MCP" (Angie Jones, Agentic AI Foundation): aaif.io/blog/skills-over-mcp/ — "Ship the manual with the product": bundle Agent Skills with MCP servers so agents get both tools and instructional guidance. Describes the working group's proposal (SEP-2640) —
skill://resources, askill://index.jsoncatalog for lightweight discovery, and progressive disclosure of full instructions on demand - "Progressive Discovery in MCP, Part 2" (Sam Morrow, GitHub MCP Server maintainer): sam-morrow.com/blog/progressive-discovery-in-mcp-part-2 — Advocates skills-based progressive discovery to solve tool bloat:
skill://resources, deferred tool loading via provider mechanisms (Anthropictool_reference, OpenAIdefer_loading), and theio.modelcontextprotocol/toolsmetadata namespace. Grounded in lessons from GitHub's MCP Server (100+ tools, 12M weekly calls) - Conceptual spec visualization (Keith Groves): enact-465fb1fc.mintlify.app/specification/draft/server/skills — "What if" exploration
- llms.txt convention: llmstxt.org — Convention for making documentation LLM-accessible; used by MCPDoc in a way similar to how skills work
- AWS Agent SOPs: docs.aws.amazon.com/…/agent-sops — Pre-built operational workflows as skill-like guidance
- Video background: youtube.com/watch?v=CEvIs9y1uog