feat(everything): add SEP-1686 Tasks support by olaservo · Pull Request #3193 · modelcontextprotocol/servers

olaservo · 2026-01-09T13:55:04Z

Description

Add support for SEP-1686 Tasks to the Everything Server. This enables the server to demonstrate MCP's task-based execution pattern for long-running operations, including task lifecycle management, status polling, and the input_required flow.

This PR demonstrates both directions of MCP Tasks:

Client → Server: Server executes tool calls as background tasks
Server → Client: Client executes sampling/elicitation requests as background tasks

Server Details

Server: everything
Changes to: tools, server capabilities, documentation

Motivation and Context

This addresses issue #3037 - adding Tasks support to the Everything Server as part of the SEP-1686 implementation.

The Everything Server serves as a reference implementation demonstrating MCP capabilities. With Tasks now part of the MCP specification (2025-11-25 schema), the Everything Server should demonstrate this feature to help client developers understand and test their Tasks implementations.

Server-side Tasks (Client calls Server)

Task creation via tools/call with task parameter
Status polling via tasks/get with statusMessage updates
Result retrieval via tasks/result
The input_required status flow with elicitation side-channel
Task TTL and cleanup

Client-side Tasks (Server calls Client) - Bidirectional

Server sends sampling/createMessage with task metadata
Client creates task and returns CreateTaskResult
Server polls tasks/get for status updates
Server retrieves result via tasks/result
Same pattern for elicitation/create

How Has This Been Tested?

✓ Tested bidirectional task flow with ad-hoc MCP client library
✓ Server-side tasks (simulate-research-query) tested with MCP Inspector v0.18.0
✓ Client-side tasks (trigger-sampling-request-async, trigger-elicitation-request-async) tested with Inspector task support branch

Breaking Changes

None.

Types of changes

Bug fix (non-breaking change which fixes an issue)
New feature (non-breaking change which adds functionality)
Breaking change (fix or feature that would cause existing functionality to change)
Documentation update

Checklist

I have read the MCP Protocol Documentation
My changes follows MCP security best practices
I have updated the server's README accordingly
I have tested this with an LLM client (MCP Inspector)
My code follows the repository's style guidelines
New and existing tests pass locally
I have added appropriate error handling
I have documented all environment variables and configuration options

Additional context

Review Feedback Applied

Per spec review, the following changes were made:

Task metadata is placed at params.task (not params._meta.task)
pollInterval is only returned in task results, not sent in requests

Known Limitations

HTTP Transport Elicitation: The input_required flow with elicitation currently works on STDIO transport but gracefully degrades on HTTP transports. On HTTP, when elicitation would be needed (e.g., simulate-research-query with ambiguous: true), the tool uses a default interpretation and continues the task rather than blocking.

This is because sendRequest for elicitation over HTTP requires SDK streaming support that isn't yet available in the released SDK. The tool detects this and falls back gracefully.

Follow-up: #3228 tracks enabling full HTTP elicitation support once the SDK adds the necessary streaming API.

Files Changed

src/everything/server/index.ts
- Import InMemoryTaskStore and InMemoryTaskMessageQueue from SDK experimental
- Create task store and message queue instances
- Add tasks capability with list, cancel, and requests.tools.call
- Add cleanup call for task store timers
src/everything/tools/simulate-research-query.ts (new)
- Demonstrates experimental.tasks.registerToolTask() API
- Simulates a multi-stage research operation with progress updates
- Shows input_required flow when ambiguous: true is passed
- Uses elicitation to gather clarification from user
src/everything/tools/trigger-sampling-request-async.ts (new)
- Demonstrates bidirectional tasks (server → client)
- Sends sampling request with task metadata
- Polls client's tasks/get for status
- Retrieves LLM result via tasks/result
- Requires client to support tasks.requests.sampling.createMessage
src/everything/tools/trigger-elicitation-request-async.ts (new)
- Same pattern as sampling for elicitation requests
- Useful when user input may take time
- Requires client to support tasks.requests.elicitation.create
src/everything/tools/index.ts
- Import and register all new task-related tools
src/everything/docs/features.md
- Added new tools to Tools section
- Added "Tasks (SEP-1686)" section documenting both task directions
- Added bidirectional task flow table and explanation

Bidirectional Task Flow

Direction	Request Type	Task Executor	Demo Tool
Client → Server	`tools/call`	Server	`simulate-research-query`
Server → Client	`sampling/createMessage`	Client	`trigger-sampling-request-async`
Server → Client	`elicitation/create`	Client	`trigger-elicitation-request-async`

Related PRs/Issues

Closes Add Support for SEP-1686: Tasks to Everything Server #3037
Related: SEP-1686 Proposal
Related: TypeScript SDK Tasks implementation
Follow-up: Enable full HTTP elicitation support after SDK streaming API is available #3228 (HTTP elicitation support)

- Add tasks capability with list, cancel, and requests.tools.call - Add InMemoryTaskStore and InMemoryTaskMessageQueue from SDK experimental - Add simulate-research-query tool demonstrating task lifecycle - Task demonstrates working -> input_required -> completed status flow - Uses elicitation for ambiguous queries when client supports it Closes modelcontextprotocol#3037 🦉 Generated with [Claude Code](https://claude.ai/code)

Add tools that demonstrate bidirectional MCP tasks where the server sends requests to the client for async execution: - trigger-sampling-request-async: Send sampling request with task params, client creates task and executes LLM call in background, server polls for completion and retrieves result - trigger-elicitation-request-async: Same pattern for user input, useful when user may take time to fill out forms Both tools: - Check client capabilities (tasks.requests.sampling/elicitation) - Accept both CreateTaskResult and direct result responses - Poll tasks/get for status updates - Fetch final result via tasks/result Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Instead of waiting for the client to call tasks/result to trigger elicitation, the server now sends elicitation/create directly from the background process using sendRequest. This simplifies the flow: - Server sends elicitation proactively when clarification is needed - Client receives and handles it via existing elicitation handler - Task resumes and completes after receiving the response - Client's polling sees completed status This approach avoids requiring the client to detect input_required status and call tasks/result as a side-channel. Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Update documentation to reflect that simulate-research-query now sends elicitation requests directly from the background task instead of using the tasks/result side-channel approach. Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Implement graceful degradation for elicitation on HTTP transport: - STDIO: Full elicitation works via sendRequest - HTTP: Catches elicitation failure, uses default interpretation - Task completes successfully on both transports simulate-research-query now uses try-catch around sendRequest and includes explanatory message when elicitation is skipped on HTTP. Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

cliffhall

The location of the task property in the elicitation and sampling request is misplaced. left suggestions.

src/everything/docs/features.md

src/everything/tools/trigger-sampling-request-async.ts

src/everything/tools/trigger-elicitation-request-async.ts

Co-authored-by: Cliff Hall <cliff@futurescale.com>

cliffhall

Sorry I didn't catch this before.

src/everything/tools/trigger-elicitation-request-async.ts

src/everything/tools/trigger-sampling-request-async.ts

…m requests - Use params.task instead of params._meta.task for task metadata - Remove pollInterval from task requests (only available on result) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

cliffhall · 2026-01-22T03:07:34Z

Async elicitation and sampling work with the Inspector PR for tasks

cliffhall

LGTM! 👍

olaservo requested a review from cliffhall January 9, 2026 13:55

cliffhall mentioned this pull request Jan 15, 2026

Add Tasks support modelcontextprotocol/inspector#1013

Merged

17 tasks

Merge branch 'main' into add-tasks-support

6556e33

olaservo marked this pull request as ready for review January 17, 2026 21:07

olaservo added the server-everything Reference implementation for the Everything MCP server - src/everything label Jan 17, 2026

olaservo and others added 5 commits January 17, 2026 17:42

Merge branch 'main' into add-tasks-support

73f0c8b

Merge branch 'main' into add-tasks-support

c20c017

cliffhall requested changes Jan 22, 2026

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Apply suggestions from code review

a160653

Co-authored-by: Cliff Hall <cliff@futurescale.com>

cliffhall requested changes Jan 22, 2026

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fix(everything): move task to params.task and remove pollInterval fro…

1542b65

…m requests - Use params.task instead of params._meta.task for task metadata - Remove pollInterval from task requests (only available on result) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

olaservo requested a review from cliffhall January 22, 2026 14:46

cliffhall approved these changes Jan 22, 2026

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cliffhall merged commit eedb060 into modelcontextprotocol:main Jan 22, 2026
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feat(everything): add SEP-1686 Tasks support#3193

feat(everything): add SEP-1686 Tasks support#3193
cliffhall merged 10 commits intomodelcontextprotocol:mainfrom
olaservo:add-tasks-support

olaservo commented Jan 9, 2026 •

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olaservo commented Jan 9, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Description

Server Details

Motivation and Context

Server-side Tasks (Client calls Server)

Client-side Tasks (Server calls Client) - Bidirectional

How Has This Been Tested?

Breaking Changes

Types of changes

Checklist

Additional context

Review Feedback Applied

Known Limitations

Files Changed

Bidirectional Task Flow

Related PRs/Issues

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cliffhall commented Jan 22, 2026

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olaservo commented Jan 9, 2026 •

edited

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