* 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
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* 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
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* 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)
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* 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>
* Fix touch gesture conflicts in WebGL example apps on mobile
* Format with prettier
* fix(examples): improve mobile support for map, pdf, and threejs examples
- map-server: fullscreen button respects safe area insets, hover/opacity
pattern with always-visible on touch devices
- pdf-server: fit-to-width scale for narrow viewports, responsive toolbar
with compact controls on mobile, safe area in fullscreen toolbar via
CSS custom properties
- threejs-server: fullscreen button respects safe area and always visible
on touch, ResizeObserver for responsive width, host containerDimensions
for fullscreen height, no container padding in fullscreen, replace
useHostStyles with inline style application to avoid overwriting
onhostcontextchanged handler
- Add `.gitignore` files to all 19 examples (`node_modules/`, `dist/`)
- Replace custom `log` objects with standard `console` methods
- Add `ontoolcancelled` handler to all `basic-server-*` examples
- Add host styling integration (`applyDocumentTheme`, `applyHostFonts`,
`applyHostStyleVariables`) to non-React `basic-server-*` examples
- Add section headers for better code organization in feature examples
- Update READMEs with Build System section explaining single-file
bundling
These changes make examples more consistent and easier to adapt.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
* feat: publish example servers to npm
Make example MCP App servers publishable to npm under the
@modelcontextprotocol scope:
- server-basic-react
- server-basic-vanillajs
- server-budget-allocator
- server-cohort-heatmap
- server-customer-segmentation
- server-scenario-modeler
- server-system-monitor
- server-threejs
- server-wiki-explorer
Changes:
- Remove `private: true` from example package.json files
- Add proper npm metadata (description, repository, license, files)
- Update ext-apps dependency from relative to ^0.2.2
- Copy server-utils.ts into each package for standalone use
- Add publish-examples job to npm-publish.yml workflow
The examples will be published automatically when a GitHub release
is created, after the main SDK package is published.
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* feat: publish examples with pkg-pr-new for PR testing
* feat: export createServer from example servers
* style: format integration-server/server.ts
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* fix: update e2e snapshots for basic-server examples
Update golden screenshots for basic-react and basic-vanillajs after
the tool output was simplified from JSON to plain text in #182.
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* merge
* refactor: update sheet-music-server and video-resource-server to new publishing pattern
- Move server-utils.ts from src/ to root level
- Add npm publishing metadata (scoped name, repository, license, files)
- Change ext-apps dependency from local to versioned ^0.2.2
- Update server.ts to handle stdio mode inline
* update package-lock
* fix: update package-lock.json for renamed server packages
* feat: add NASA public domain video to video-resource-server
Added 'nasa-earth' option - NASA ISS Earth observations (6.4MB).
Source: archive.org/details/NASA-Ultra-High-Definition (public domain)
* fix: add default videoId for video-resource-server
* fix: use existing bunny-1mb as default video, remove nasa-earth
* refactor: update new framework examples to publishing pattern
Add publishing metadata for:
- @modelcontextprotocol/server-basic-preact
- @modelcontextprotocol/server-basic-solid
- @modelcontextprotocol/server-basic-svelte
- @modelcontextprotocol/server-basic-vue
Changes:
- Move server-utils.ts from src/ to root
- Add npm publishing metadata
- Update ext-apps dep to versioned ^0.2.2
- Add stdio mode support in main()
* fix: add missing @rollup/rollup-win32-arm64-msvc to optionalDependencies
This fixes the Windows ARM64 CI build failure caused by npm's optional
dependency bug. The package.json was missing this platform-specific
rollup binding.
---------
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Co-authored-by: Olivier Chafik <ochafik@anthropic.com>
Apply host-provided safe area insets as padding on main containers
across all examples. This ensures content doesn't render under
system UI elements like phone notches.
React apps use `useState` + `onhostcontextchanged` handler with
initial fetch via `getHostContext()` in `useEffect`. Vanilla JS
apps apply padding in the handler and invoke it after `connect()`.
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* Centralize example server transport logic in shared utils
Move stdio/HTTP transport handling into `server-utils.ts` so example
servers only need to call `startServer(createServer)`. Switch HTTP
transport to stateless mode and remove legacy SSE endpoints.
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* Make example servers self-contained with local server-utils
Copy `server-utils.ts` into each example's `src/` directory so examples
can be used standalone without the shared directory. Updates imports
from `"../shared/server-utils.js"` to `"./src/server-utils.js"`.
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* Add `integration-server` example for E2E testing
Add dedicated `integration-server` example (duplicated from
`basic-server-react`) to preserve E2E testing capabilities while
allowing `basic-server-react` to be simplified as a minimal example.
Changes:
- Add `examples/integration-server` exercising SDK communication APIs
- Update E2E tests to use `integration-server` instead of
`basic-server-react` and `basic-server-vanillajs`
- Use server name labels instead of indices for more robust test
selection
- Remove `basic-react.png` and `basic-vanillajs.png` golden snapshots
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* Simplify `basic-server-*` examples
- Clarify comments
- Return plain text from `get-time` tool instead of JSON
- Remove simulated cleanup delay from `onteardown`
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---------
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
* refactor: rename request methods to remove send prefix
Following the MCP TS SDK convention where request methods don't have
the "send" prefix (reserved for notifications):
- App.sendMessage() → App.message()
- App.sendOpenLink() → App.openLink()
- AppBridge.sendResourceTeardown() → AppBridge.resourceTeardown()
The old method names are kept as deprecated aliases for backwards
compatibility.
Updated all examples to use the new method names.
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* test: add tests for deprecated method aliases
- Update existing tests to use new method names (message, openLink)
- Add tests verifying deprecated aliases are same reference as new methods
- Add tests verifying deprecated aliases still work functionally
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* refactor: rename message→sendMessage, resourceTeardown→teardownResource
- App.message() → App.sendMessage() (with deprecated message alias)
- AppBridge.resourceTeardown() → AppBridge.teardownResource() (with deprecated aliases)
This better follows the pattern where methods that send data have 'send' or action verb prefix.
* fix: update examples to use sendMessage instead of message
* fix: update basic-host to use teardownResource
* fix: update threejs-server to use sendMessage
* refactor: remove deprecated app.message alias
The app.message alias was removed since sendMessage is the correct name.
sendResourceTeardown already exists in AppBridge.
* refactor: remove resourceTeardown alias, keep only sendResourceTeardown
---------
Co-authored-by: Claude <noreply@anthropic.com>
* feat: add server helpers and optional connect() transport
Add `src/server/` with convenience functions for registering MCP App tools
and resources:
- `registerAppTool(server, name, config, handler)`
- `registerAppResource(server, name, uri, config, callback)`
The `transport` parameter in `App.connect()` is now optional, defaulting to
`PostMessageTransport(window.parent)`.
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* Update src/server/index.ts
Co-authored-by: Jonathan Hefner <jonathan@hefner.pro>
* fix: refine server helper types
- Make RESOURCE_URI_META_KEY required in McpUiAppToolConfig (tools need a UI resource)
- Make _meta optional in McpUiAppResourceConfig (not all resources need custom metadata)
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* refactor: simplify RESOURCE_URI_META_KEY re-export
* refactor: consolidate export statements
---------
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Co-authored-by: Jonathan Hefner <jonathan@hefner.pro>
Interactive Wikipedia link graph visualization using force-graph with:
- Force-directed graph layout for exploring page connections
- Node expansion to reveal first-degree Wikipedia links
- Visual state tracking (blue=default, green=expanded, red=error)
- Direct browser access to Wikipedia pages
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Andrew Khadder
Olivier Chafik
Mel Ludowise
Jonathan Hefner
Jerome