* feat: Add tool registration and bidirectional tool support
This PR adds comprehensive tool support for MCP Apps, enabling apps
to register their own tools and handle tool calls from the host.
- Add `registerTool()` method for registering tools with input/output schemas
- Add `oncalltool` setter for handling tool call requests from host
- Add `onlisttools` setter for handling tool list requests from host
- Add `sendToolListChanged()` for notifying host of tool updates
- Registered tools support enable/disable/update/remove operations
- Add `sendCallTool()` method for calling tools on the app
- Add `sendListTools()` method for listing available app tools
- Fix: Use correct ListToolsResultSchema (was ListToolsRequestSchema)
- Add comprehensive tests for tool registration lifecycle
- Add tests for input/output schema validation
- Add tests for bidirectional tool call communication
- Add tests for tool list change notifications
- All 27 tests passing
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
* nits
* Update apps.mdx
* feat: Add automatic request handlers for app tool registration
Implement automatic `oncalltool` and `onlisttools` handlers that are
initialized when apps register tools. This removes the need for manual
handler setup and ensures tools work seamlessly out of the box.
- Add automatic `oncalltool` handler that routes calls to registered tools
- Add automatic `onlisttools` handler that returns full Tool objects with JSON schemas
- Convert Zod schemas to MCP-compliant JSON Schema using `zod-to-json-schema`
- Add 27 comprehensive tests covering automatic handlers and tool lifecycle
- Test coverage includes error handling, schema validation, and multi-app isolation
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
* type updates
* fix: Ensure tools/list returns valid JSON Schema for all tools
- Always return inputSchema as object (never undefined)
- Keep filter for enabled tools only in list
- Update test to match behavior (only enabled tools in list)
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
* type updates
* rm zod-to-json-schema
* fix: Update RegisteredTool to use 'handler' instead of 'callback' (SDK API change)
* refactor: Rename sendCallTool/sendListTools to callTool/listTools
Avoid double-verb naming pattern for consistency with existing API.
* feat: Add screenshot and click support to SDK
- Add McpUiScreenshotRequest/Result and McpUiClickRequest/Result types
- Add onscreenshot and onclick handlers to App class
- Add screenshot() and click() methods to AppBridge class
- Generate updated Zod schemas
* feat(map-server): Enable registerTool with navigate-to and get-current-view
- Uncomment and fix the navigate-to tool for animated navigation
- Add get-current-view tool to query camera position and bounding box
- Add flyToBoundingBox function for smooth camera animation
- Add setLabel function for displaying location labels
* feat(pdf-server): Add widget interaction tools
- get-document-info: Get title, current page, total pages, zoom level
- go-to-page: Navigate to a specific page
- get-page-text: Extract text from a page
- search-text: Search for text across the document
- set-zoom: Adjust zoom level
* feat(shadertoy-server): Add widget interaction tools
* feat(examples): Add widget interaction tools to budget-allocator, shadertoy, wiki-explorer, and threejs
budget-allocator:
- get-allocations: Get current budget allocations
- set-allocation: Set allocation for a category
- set-total-budget: Adjust total budget
- set-company-stage: Change stage for benchmarks
- get-benchmark-comparison: Compare against benchmarks
shadertoy:
- set-shader-source: Update shader source code
- get-shader-info: Get shader source and compilation status
- Sends errors via updateModelContext
wiki-explorer:
- search-article: Search for Wikipedia articles
- get-current-article: Get current article info
- highlight-node: Highlight a graph node
- get-visible-nodes: List visible nodes
threejs:
- set-scene-source: Update the Three.js scene source code
- get-scene-info: Get current scene state and any errors
- Sends syntax errors to model via updateModelContext
* feat: Add expand-node tool to wiki-explorer and update tool descriptions
Wiki Explorer:
- Add expand-node tool - the critical missing tool for graph exploration
- Claude can now programmatically expand nodes to discover linked articles
Server descriptions updated to mention widget tools:
- map-server: navigate-to, get-current-view
- pdf-server: go-to-page, get-page-text, search-text, set-zoom, get-document-info
- budget-allocator: get-allocations, set-allocation, set-total-budget, etc.
- shadertoy: set-shader-source, get-shader-info
- wiki-explorer: expand-node, search-article, highlight-node, etc.
All descriptions now mention 'Use list_widget_tools to discover available actions.'
* refactor: Simplify tool descriptions - remove client implementation details
The server tool descriptions now just mention that widgets are interactive
and can be controlled, without teaching the model about list_widget_tools
(which is the client's responsibility to teach).
Before: 'The widget exposes tools: X, Y, Z. Use list_widget_tools to discover...'
After: 'The widget is interactive and exposes tools for X and Y.'
* Remove ui/screenshot and ui/click protocol methods
These will be proposed separately from the app tool registration changes.
* fix(app): auto-register tools capability in registerTool
When registerTool is called before connect() on an App created without
explicit tools capability, setRequestHandler's capability assertion
would throw, breaking app initialization at module load.
Auto-register { tools: { listChanged: true } } on first registerTool
call (pre-connect only), mirroring McpServer.registerTool behavior.
Fixes pdf-annotations e2e failures where the PDF canvas never rendered
because registerTool threw at module scope.
* pdf-server: replace app-tools with 1:1 interact command mapping
Converts the 5 placeholder app-registered tools into 12 tools that map
directly to the server's interact commands (navigate, search, find,
search_navigate, zoom, add_annotations, update_annotations,
remove_annotations, highlight_text, fill_form, get_text, get_screenshot)
plus the existing get-document-info.
Implementation stays DRY by dispatching through the existing
processCommands() handler — each tool callback constructs a PdfCommand
and runs it via a small runCommand() wrapper. For get_text and
get_screenshot, the page-data collection is extracted from
handleGetPages into a shared collectPageData() helper so results can
be returned directly instead of round-tripping through the server.
Tool names and zod schemas mirror the interact command parameter shapes
from server.ts so the model sees the same surface whether it goes
through interact or app-tools. The server-side interact tool is
unchanged and remains available for hosts without app-tool support.
* chore: drop unused test vars and stale Request/Result imports
* docs(spec): address review feedback on app tool registration
- Add outputSchema to Tool struct (matches SDK + core MCP)
- Reword "black box" bullets: drop stale screenshots reference, clarify no DOM access
- Clarify push vs pull contrast with explicit setWidgetState + ui/update-model-context refs
- Add Task-reference future-work bullet for tools outliving render lifecycle
* docs(spec): clarify app DOM is not host-introspectable; frame tools as pull complementing update-model-context push
* fix(app): emit title and omit absent outputSchema in tools/list
* feat(app): accept Standard Schema in registerTool/registerAppTool
App.registerTool and registerAppTool now accept any schema implementing
the Standard Schema spec (Zod ≥3.25, ArkType, Valibot, …) instead of
zod-only. Uses ~standard.validate / ~standard.jsonSchema directly, so
app.ts no longer imports zod at runtime — zod is now an optional peer.
Mirrors the StandardSchemaWithJSON type from
modelcontextprotocol/typescript-sdk#1689 so bumping to SDK v2 is a
drop-in import swap. Adds @standard-schema/spec (types-only) and a
hand-rolled non-zod test.
* docs(spec): reference core MCP Tasks for long-running app tools
App tools/call MAY be task-augmented per the core MCP Tasks utility
(spec 2025-11-25). Adds a Long-Running App Tools subsection: hosts proxy
tasks/* while the app is mounted; apps SHOULD delegate long-lived work
to the server so the task survives iframe teardown. Removes the stale
'future extension' bullet — Tasks is shipped.
* docs(spec): note Schema Validation accepts any Standard Schema library
* chore: clean unused-var and no-op-await diagnostics in app.ts and tests
* refactor(app): fold error prefix into validateStandardSchema; clarify registerAppTool runtime caveat
* chore(typedoc): mark RequestHandlerExtra as intentionally not exported
AppToolCallback (introduced with the Standard Schema migration) references
the local RequestHandlerExtra alias in its parameter type. The alias is a
private Parameters<> derivation and isn't part of the public API surface,
so add it to intentionallyNotExported alongside AppOptions/MethodSchema.
* fix(app): restore zod v3.25 compat via lazy z.toJSONSchema fallback
zod v3.25.x implements ~standard.validate but not ~standard.jsonSchema,
so constraining to StandardSchemaWithJSON broke the ^3.25.0 peer range.
Widen registerTool to StandardSchemaV1 and fall back to a lazy zod/v4
import for serialization when ~standard.jsonSchema is absent and
vendor==='zod'. Non-zod schemas without jsonSchema get a clear error.
* docs(spec): slim Long-Running App Tools to a pointer into core MCP Tasks
* chore: add TODO(sdk-v2) marker in standard-schema.ts
* fix(app): align registerTool runtime with declared types
- Handler reads registeredTool.{input,output}Schema so update() takes effect
- Call cb(extra) when no inputSchema, matching AppToolCallback<undefined>
- Throw on duplicate name; guard list_changed pre-connect; notify on register
- Drop misleading zod optional peer (still required by generated/schema.ts)
- examples: fix pdf search/find stale match count; threejs set-scene-source re-render
- spec: Zod → Standard Schema; clarify tools availability via tools/list after init
* feat(app): type structuredContent from outputSchema in registerTool
AppToolCallback gains an Out param: when outputSchema is provided,
structuredContent is required and typed via StandardSchemaV1.InferOutput,
with an `isError: true` escape hatch. Without outputSchema, return type
is unchanged (CallToolResult). Uses intersection rather than Omit since
CallToolResult's index signature swallows Omit's known keys.
Also drops the `as any` casts on z.object(...) in tests — zod 4 satisfies
StandardSchemaV1 directly.
* fix(app): registerTool edge cases + example tool correctness
App.registerTool:
- Skip outputSchema validation when result.isError (matches AppToolResult type)
- Pin callback arity to original config.inputSchema; only the validation schema is mutable via update()
- Default missing tools/call arguments to {}
- remove() is a no-op if the handle is stale (re-registered or already removed)
- Gate list_changed notifications on the listChanged capability
Examples:
- threejs: propagate executeThreeCode failures to onSceneError/onSceneRendering; catch updateModelContext rejection
- wiki-explorer: search-article preserves graph on no-match
- budget-allocator: fix category/stage values in tool descriptions
* feat(app,app-bridge): guard requests sent before handshake completes (#620)
* feat(app,app-bridge): guard requests sent before handshake completes
Calling host-bound methods before the ui/initialize →
ui/notifications/initialized handshake completes can race the handshake
on strict hosts and leave the iframe permanently hidden.
App (View side):
- All 8 host-bound methods (callServerTool, readServerResource,
listServerResources, sendMessage, updateModelContext, openLink,
downloadFile, requestDisplayMode) now check that connect() has sent
the initialized notification.
- New AppOptions.strict (default false): console.error when false,
throw when true. AppOptions is now exported.
- useApp() forwards strict to the App constructor.
- Flag resets on reconnect.
AppBridge (Host side):
- replaceRequestHandler is overridden to wrap every host-bound handler
with a console.warn if the request arrives before
ui/notifications/initialized. Never throws. ui/initialize and ping
use setRequestHandler directly and are exempt; notifications are
unaffected.
- Catches Views that hand-roll postMessage without the SDK.
- Flag resets on reconnect.
Refs anthropics/claude-ai-mcp#61, anthropics/claude-ai-mcp#149.
* fix(docs): drop AppOptions from intentionallyNotExported now that it is exported
---------
Co-authored-by: Claude <noreply@anthropic.com>
* feat: MCP app sampling support via stock SDK types
Alternative to #477. Instead of forking a stripped-down sampling schema,
this reuses the stock `CreateMessageRequest` / `CreateMessageResult` /
`CreateMessageResultWithTools` types from `@modelcontextprotocol/sdk`
directly — same pattern already used for `tools/call`.
- Spec: `sampling/createMessage` listed under `### Standard MCP Messages`,
`sampling?: { tools?: {} }` added to `HostCapabilities` (mirrors MCP
`ClientCapabilities.sampling` shape for easy pass-through).
- SDK: `App.createSamplingMessage()` with overloads that narrow the return
type based on whether `params.tools` is set; `AppBridge.oncreatesamplingmessage`
setter; `CreateMessageRequest`/`CreateMessageResult*` added to the
`AppRequest`/`AppResult` unions.
- Picks up SEP-1577 tool-calling support (`tools`, `toolChoice`, `tool_use`
content blocks, `stopReason: "toolUse"`, array content) for free — unblocks
the "nested agents" use case motivated by the original PR.
https://claude.ai/code/session_01ENGWTtsfcyP4S6fTWtUMAh
* feat(app): guard createSamplingMessage before handshake completes
---------
Co-authored-by: Claude <noreply@anthropic.com>
* feat(events): DOM-model on* semantics with addEventListener/removeEventListener
Fixes#551 (useHostStyles broken: fonts clobber theme/CSS variables)
Fixes#225 (user onhostcontextchanged and SDK hooks mutually exclusive)
The on* setters now follow the DOM event model:
- Replace semantics (like el.onclick) with getters
- Coexist with addEventListener/removeEventListener listeners
- Both channels fire on dispatch: on* handler then listeners
Introduces ProtocolWithEvents base class between Protocol and
App/AppBridge. Each notification event gets a slot with two independent
channels (singular on* handler + addEventListener listener array).
useHostStyles hooks now use addEventListener with proper cleanup,
so they compose correctly with user on* handlers.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
* Fix typedoc validation warnings
- Export AppEventMap, AppBridgeEventMap, ProtocolWithEvents so they
appear in generated docs (they're part of public addEventListener
signatures)
- Move AppBridgeEventMap above the AppBridge class JSDoc — it had been
inserted between the doc block and the class, orphaning the AppBridge
docs onto the wrong type
- Drop @param callback tags from on* getter/setter pairs — typedoc
attaches the doc block to the getter signature which has no params
- Add MethodSchema to intentionallyNotExported (internal zod helper
referenced by the now-documented eventSchemas field)
---------
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Follow-up to #470. Matches MCP SDK Client.listResources(params?) signature
so callers can omit the empty {} for the common case.
Also reflows a line in app-bridge.test.ts that prettier flagged.
- Rename "host styling" section to "host context" and add safe area
insets handling
- Replace abstract `renderLoadingUI`/`renderFinalUI` example with
concrete code preview pattern for `ontoolinputpartial`
- Rename callback parameter `params` → `ctx` for clarity across all
`onhostcontextchanged` handlers
- Add CSS snippet for fullscreen border-radius handling
- Expand display mode example to show `availableDisplayModes` check
- Fix minor typos and wording consistency
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Add explicit backtick-wrapped display text to all `{@link}` tags for
monospace rendering in TypeDoc output. This improves readability by:
- Using monospace font for code references (types, methods, functions)
- Stripping module prefixes from display text (e.g., `app!App.connect`
displays as `App.connect`)
Updated files across the SDK including `App`, `AppBridge`,
`PostMessageTransport`, React hooks, server helpers, types, and
documentation.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Add new pattern showing how to combine `updateModelContext()` with
`sendMessage()` when data exceeds message size limits. The example
demonstrates offloading a large transcript to model context first,
then sending a brief trigger message.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Documents `updateModelContext` for keeping the model informed about user
interactions. The example shows a shopping cart use case with YAML frontmatter
for structured, parseable context.
Also refines the `updateModelContext` JSDoc to clarify the difference from
`sendMessage` and removes the `structuredContent` example.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Adds JSDoc example `App_updateModelContext_reportError` showing how to
report runtime errors (e.g., microphone permission denied) back to the
model using `updateModelContext`.
Updates patterns.md with clearer framing:
- Server-side (tool handler): return `{ isError: true, ... }`
- Client-side (app): use `updateModelContext` for runtime errors
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
- Expand `App_ontoolinputpartial_progressiveRendering` example in
`app.examples.ts` to show full state management pattern with
`toolInputs` and `toolInputsPartial` variables
- Add healed JSON caveat to `ontoolinputpartial` JSDoc in `app.ts`
- Update `patterns.md` to reference the expanded example and document
the streaming preview pattern
- Remove empty `lowerPerceivedLatency` placeholder from `patterns.tsx`
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Add `App_onhostcontextchanged_respondToDisplayMode` example showing how to
listen for display mode changes and update UI with `classList.toggle()`.
Update `App_requestDisplayMode_fullscreen` to `App_requestDisplayMode_toggle`
to show the common toggle pattern checking `availableDisplayModes` first.
Refactor full examples (pdf-server, shadertoy-server) to use
`classList.toggle(class, condition)` instead of add/remove branches.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Follow-up to the examples extraction: pass dependencies as function
parameters instead of using global stub declarations, rename region
names to match method names (e.g., `AppBridge_guestCapabilities_*` →
`AppBridge_getAppCapabilities_*`), and simplify examples using optional
chaining.
Also clarifies `RESOURCE_URI_META_KEY` documentation to indicate it's
for tool definition metadata (from `tools/list`), not tool result
metadata, and removes the redundant `setNotificationHandler` example
in favor of the simpler event setter approach.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Extract inline code examples from JSDoc comments into companion
`.examples.ts`/`.examples.tsx` files. Examples are now:
- Type-checked by wrapping them in functions
- Referenced via `{@includeCode ./file.examples.ts#regionName}` tags
- Organized using `//#region` and `//#endregion` markers
This keeps the main source files cleaner while ensuring examples
compile correctly. Updated TypeDoc config with `exampleTag: false`
to support title text on `@example` tags.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
