* 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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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
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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)
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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>
* Clarify spec and SDK: accept UIResourceMeta in both resources/list and resources/read
The spec defines UIResource with _meta.ui, implicitly as an extension of the Resource type (resources/list), but examples and practice place _meta.ui on TextResourceContents (resources/read). The registerAppResource helper accepts _meta.ui in its config (which ends up in resources/list), but examples only return said _meta.ui from resources/read — and current hosts might be just ignoring it.
This change:
- Adds a 'Metadata Location' subsection to the draft spec explicitly stating that _meta.ui is valid on both the resource listing entry AND the content item, with content-item taking precedence.
- Updates the spec example to show _meta on the resource declaration (resources/list).
- Updates the CSP construction example to reference both locations.
- Clarifies McpUiAppResourceConfig JSDoc: _meta here appears in resources/list and serves as a listing-level fallback for when content items omit _meta.ui.
- Fixes the map-server example comment that incorrectly stated _meta must only be on the content item.
* Add McpUiReadResourceResult type for UI metadata in resources/read
* basic-host: support UIResourceMeta fallback from resources/list
---------
Co-authored-by: Claude <noreply@anthropic.com>
* docs: standardize UI terminology to use "view" consistently
Replaces "widget" and "Guest UI" terminology with "view" across
the codebase as decided in the community survey.
This change updates:
- Specification document
- SDK source code and JSDoc comments
- Example servers and documentation
- Plugin documentation and skills
Closes#71
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
* fix(examples): resolve DIST_DIR path for npm package execution
When servers are compiled to dist/server.js and published to npm,
`import.meta.dirname` already points to dist/, so joining with "dist"
results in dist/dist/ which doesn't exist.
This fix detects whether we're running from TypeScript source or
compiled JavaScript and adjusts the path accordingly:
- From source (server.ts): use dist/ subdirectory
- From compiled (dist/server.js): use current directory
Fixes ENOENT errors like:
"ENOENT: no such file or directory, open '.../dist/dist/mcp-app.html'"
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
* fix(pdf-server): mark pdfjs-dist as external in bundle
The pdf.worker.mjs file wasn't being found when running from npm
because bun bundled pdfjs-dist but didn't include the worker file.
By marking pdfjs-dist as external, it uses the installed package
from node_modules at runtime where the worker is available.
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---------
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
* feat: compile example servers to JavaScript for npm consumption
Add TypeScript compilation for server code so the example packages can be
imported and used by consumers without requiring TypeScript compilation.
Changes:
- Add tsconfig.server.json to each example for compiling server code
- Update package.json exports to point to compiled dist/server/server.js
- Add types field pointing to dist/server/server.d.ts
- Update build scripts to include server compilation step
- Fix .ts import extensions to .js in customer-segmentation-server
This enables importing the createServer function from published packages:
import { createServer } from '@modelcontextprotocol/server-basic-react';
* fix: add type assertion for Nominatim API response
* chore: regenerate schemas
* refactor: split server examples into library and binary entry points
- server.ts: exports createServer() only (library entry point)
- main.ts: entry point with main() that runs the server (binary)
- package.json: adds bin field for npx support, uses inline bun build
- tsconfig.server.json: emitDeclarationOnly, outputs to dist/
This allows:
1. Importing the server as a library: import { createServer } from '@modelcontextprotocol/server-basic-react'
2. Running with npx: npx @modelcontextprotocol/server-basic-react [--stdio]
Added migration script at scripts/migrate-server-examples.ts
* refactor: migrate remaining server examples to library/binary structure
Apply the same refactoring to all 13 remaining server examples:
- scenario-modeler-server, shadertoy-server, map-server
- cohort-heatmap-server, customer-segmentation-server, video-resource-server
- system-monitor-server, budget-allocator-server, sheet-music-server
- threejs-server, integration-server, transcript-server, wiki-explorer-server
Each now has:
- server.ts: exports createServer() (library)
- main.ts: runs the server (binary with shebang)
- bin field in package.json for npx support
* chore: remove unused server-utils.ts from video-resource-server/src
* update
* fix(build): make Windows-compatible by removing chmod and fixing bun externals
- Remove 'chmod +x dist/index.js' which doesn't exist on Windows
- Add '--external ./server.js' to prevent bun from treating the import as a second entry point
* fix(build): use .ts import for bun compatibility
- Change import from './server.js' to './server.ts' in main.ts files
- Remove --external flag since bun should inline everything
- Fixes Windows build where bun couldn't resolve .js to .ts properly
* fix(build): use --external for Windows bun compatibility
Bun on Windows incorrectly treats imported .ts files as entry points.
Use --external './server.js' to work around this, creating a runtime
dependency between index.js and server.js.
* style: fix prettier formatting in pdf-server/main.ts
* fix(build): remove quotes from --external for Windows cmd.exe compatibility
* fix(build): use glob pattern for --external to work on all platforms
The literal path --external ./server.js was not matching the import.
Using glob pattern --external "./server*" correctly externalizes the server module.
* fix(build): use */server.js pattern for --external
The "./server*" pattern was not matching on Windows.
Using "*/server.js" matches any path ending in /server.js which works cross-platform.
* fix(build): use *server.js pattern without slash for Windows compatibility
* update package-lock
* chore: regenerate package-lock.json for cross-platform compatibility
* fix(build): use ./server.js instead of glob pattern for Windows compatibility
* fix(build): use double quotes for banner to fix Windows cmd.exe compatibility
---------
Co-authored-by: Olivier Chafik <ochafik@anthropic.com>
* map-server: fix async/await in ontoolresult, remove unused getViewStorageKey
* fix(map-server): improve updateModelContext and fix initialization
- Use structured YAML frontmatter format for model context (like pdf-server)
- Add tool name, altitude, and cleaner data format
- Fix initialization deadlock: app.connect() was inside ontoolresult handler
which could never fire until connected
- Fix view state persistence: widgetUUID now properly extracted from
ontoolresult and used to restore persisted camera position
- Server now includes widgetUUID in tool result _meta for widget identification
* fix(pdf-server): use widgetUUID for page persistence
- Add widgetUUID to tool result _meta for widget identification
- Use widgetUUID instead of generated key (pdfUrl+toolId) for localStorage
- Enables reliable page restoration when revisiting PDF widgets
* fix(transcript-server): use structured YAML frontmatter for model context
- Add tool name, listening status, and unsent entry count in frontmatter
- Consistent format with pdf-server and map-server
* update names
* drop bogus altitude
* Update mcp-app.ts
* feat: Add CesiumJS map server example
A WebGL-based 3D globe example that demonstrates:
- CesiumJS integration with MCP Apps
- CSP configuration for external tile servers
- worker-src directive usage for tile decoding
Tools:
- geocode: Search places via OpenStreetMap Nominatim
- show-map: Display interactive 3D globe at coordinates
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
* comment out app.registerTool call for now
* prettier
* fix error handling in server-utils.ts
* refactor: rename cesium-map-server to map-server
- Rename examples/cesium-map-server to examples/map-server
- Update package name to @modelcontextprotocol/server-map
- Add README.md with documentation
* style: add min-height of 400px to map container
* feat(map-server): add fullscreen support, clean UI, sharp rendering
- Add fullscreen toggle button (only shown if host supports it)
- Use autoResize: false and manually send height of 400px
- Hide Cesium UI controls (home, scene mode picker)
- Remove location label (gets stale quickly)
- Use full device pixel ratio for sharp rendering on high-DPI displays
- Resize Cesium viewer when display mode changes
* feat(map-server): add reverse geocoding (logging only) and rounded corners
- Add camera move end listener for reverse geocoding
- Debounce Nominatim API calls (1.5s) to respect rate limits
- Log location name to console on camera move
- Add nominatim.openstreetmap.org to CSP connectDomains
- Add 8px rounded corners to map container
* fix(map-server): fix pixelated rendering on high-DPI displays
- Set canvas imageRendering to 'auto' (CesiumJS defaults to pixelated)
- Set resolutionScale to window.devicePixelRatio for native resolution
* tweaks
* update model context w/ current location
* fix(map-server): improve rendering quality and add visible extent logging
Rendering fixes:
- Remove incorrect resolutionScale = devicePixelRatio which was doubling
the scaling factor on Retina displays (2x2=4x), causing blurriness
- Disable FXAA anti-aliasing which can cause blurriness on high-DPI displays
- Keep useBrowserRecommendedResolution: false to use native devicePixelRatio
Reverse geocoding improvements:
- Add getVisibleExtent() using camera.computeViewRectangle() to get the
visible bounding box (west, south, east, north)
- Add getScaleDimensions() to calculate visible area in km
- Add calculateNominatimZoom() to map visible extent to appropriate
Nominatim zoom level (3=country to 18=building)
- Log visible extent with dimensions on each camera move
- Pass zoom parameter to Nominatim for context-aware geocoding results
- Update model context with visible area dimensions
* fix(map-server): direct positioning + wait for tiles before showing
Changes:
- Remove zoom granularity logic from reverse geocoding (was not working)
- Keep extent logging in both console and model context
- Replace flyTo animation with instant setView positioning
- Add waitForTilesLoaded() to detect when tiles finish loading
- Keep loading spinner visible until:
1. Tool input positions camera to destination
2. Tiles at destination are fully loaded
- Add 5-second fallback timeout if no tool input received
- Add 10-second timeout for tile loading to prevent infinite wait
* feat(map-server): use viewbox search to find visible places
Replace center-point reverse geocoding with Nominatim viewbox search:
- Add searchPlacesInBox() that queries Nominatim with bounded viewbox
- Uses layer=address&featuretype=settlement to find cities/towns
- Returns up to 5 visible places in the current view
- Update model context with 'Visible places: City1, City2, ...'
- Still includes center coordinates and extent dimensions
This provides better context about what's actually visible on the map
rather than just the address at the center point.
* fix(map-server): use CARTO @2x retina tiles for sharp rendering
Root cause: Standard OSM tiles are 256x256 pixels. On Retina displays
(devicePixelRatio=2), these get scaled up 2x, making them look pixelated.
Solution: Switch to CARTO Voyager tiles which provide @2x retina support:
- Detect high-DPI displays using window.devicePixelRatio
- Use 512x512 tiles with @2x suffix on Retina displays
- Use 256x256 tiles on standard displays
- Set tileWidth/tileHeight to match actual tile size
- Use CARTO subdomains (a,b,c,d) for load balancing
- Update CSP to allow CARTO tile domains
CARTO Voyager provides clean OSM-based tiles with free @2x retina support,
no API key required.
* fix(map-server): use OSM tiles and fix reverse geocoding
- Switch back from CARTO to standard OSM tiles (tile.openstreetmap.org)
for better detail and label rendering
- Fix geocoding: use reverse geocode API instead of search API
(search API requires a q= parameter, returns 400 without it)
- Update CSP domains for OSM tile server
* fix(map-server): use *.openstreetmap.org wildcard in CSP
Simplify CSP to use wildcard for both tiles and geocoding:
- connectDomains: *.openstreetmap.org covers tile.* and nominatim.*
- resourceDomains: *.openstreetmap.org for tile images
* feat(map-server): multi-point sampling for visible places
- Sample multiple points in visible extent to discover places
- Adaptive sampling based on extent size:
- < 30km: center only (city zoom)
- 30-100km: center + 2 corners
- > 100km: center + 4 quadrants
- Proper rate limiting for Nominatim (1.1s between requests)
- Shows 'Visible places: City1, City2, ...' in model context
- Fix: move geocode tool registration inside createServer()
* format
* fix(map-server): fix Express listen callback + add e2e tests
- Fix incorrect Express listen() callback signature (err param doesn't exist)
- Add map-server to e2e test suite with SLOW_SERVERS timeout (5s for tiles)
- Improve comment about experimental ui/update-model-context API
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
---------
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Andrew Khadder
Olivier Chafik
Hryhorii (Greg) Avcharov
Liad Yosef
Jerome