mcp-timeout-demo

A Claude Code MCP server that exposes a long-running tool with per-tool configurable timeouts and periodic progress notifications, so Claude Code never severs the request mid-flight.

If you have ever seen Claude Code kill an MCP tool call that was otherwise healthy — because it went silent for longer than the client's default idle window — this plugin shows the smallest possible fix and ships it as a drop-in server you can install today.

Companion article: https://claudeplugins.nicedx.com/claude-code-mcp-tool-timeout-configurable-long-running/

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What you get

• One MCP tool, long_running_task, with a timeout_ms parameter validated against [1, 600_000] ms.
• Cooperative cancellation via asyncio.wait_for — a genuinely stuck call fails at the ceiling, it does not hang forever.
• Progress notifications every 250 ms via ctx.report_progress — the Claude Code client's idle timer never fires while the tool is actually working.
• Per-tool timeout defaults from an env var or a JSON config file, with env vars winning over the file.
• A ready-to-copy .mcp.json snippet at examples/claude_code.mcp.json.
• A Claude Code plugin manifest at .claude-plugin/plugin.json so the same server can install via a plugin marketplace.

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Install

The server ships as a standard Python distribution. Three install paths, in order of preference:

1. uv run (recommended, zero pre-install)

uv bootstraps a venv on the fly, so nothing has to be pre-installed globally. Drop this into your project's .mcp.json:

{
  "mcpServers": {
    "mcp-timeout-demo": {
      "command": "uv",
      "args": ["run", "mcp-timeout-demo"],
      "env": {
        "MCP_TIMEOUT_DEMO_TIMEOUT_MS__LONG_RUNNING_TASK": "60000"
      }
    }
  }
}

Then restart Claude Code in that project. That is it.

2. pip install + console script

pip install mcp-timeout-demo

Register with Claude Code:

claude mcp add mcp-timeout-demo \
  --env MCP_TIMEOUT_DEMO_TIMEOUT_MS__LONG_RUNNING_TASK=60000 \
  -- mcp-timeout-demo

3. From source

git clone https://github.com/vytharion/claude-code-mcp-tool-timeout-configurable-long-running.git
cd claude-code-mcp-tool-timeout-configurable-long-running
uv sync
uv run mcp-timeout-demo

4. As a Claude Code plugin

The repository ships a .claude-plugin/plugin.json manifest, so the server can also be published as a plugin through a Claude Code plugin marketplace. The .claude-plugin/marketplace.json in this repo is the minimal example marketplace entry — point your marketplace tooling at the repository URL and Claude Code will read both files.

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Configure

The tool has one default: DEFAULT_TIMEOUT_MS = 5_000. Two mechanisms override that default, in this precedence (most-specific wins):

Environment variable

MCP_TIMEOUT_DEMO_TIMEOUT_MS__<TOOL_NAME_UPPER>

Example — raise the ceiling for long_running_task to 60 seconds:

export MCP_TIMEOUT_DEMO_TIMEOUT_MS__LONG_RUNNING_TASK=60000

JSON config file

Set MCP_TIMEOUT_DEMO_CONFIG to point at a JSON file with this shape:

{
  "tools": {
    "long_running_task": {
      "timeout_ms": 60000
    }
  }
}

Then:

export MCP_TIMEOUT_DEMO_CONFIG=/path/to/mcp-timeouts.json

Per-call override

Clients can still pass timeout_ms on the individual call_tool request. That per-call value always wins over the default — the default only sets the ceiling the schema advertises.

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Verify

Once the server is registered, ask Claude Code to call the tool:

"Call long_running_task with label 'demo', timeout_ms=3000, and work_duration_ms=1500."

You should see the tool return:

done:demo:worked=1500ms:timeout=3000ms

To see the timeout path fire, ask for work that exceeds the deadline:

"Call long_running_task with label 'over', timeout_ms=200, and work_duration_ms=5000."

The tool returns cleanly with:

timeout:over:after=200ms

The client will also receive periodic progress notifications during either call.

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Troubleshooting

"Claude Code still says the tool timed out"

That is the client-side MCP timeout, not the tool's timeout_ms. This plugin only fixes the server-side idle-timer story via progress notifications. If Claude Code itself has a hard per-call ceiling, this plugin cannot reach past it — file a follow-up config with the client.

"The env var is not being picked up"

The env-var key encodes the tool name in upper case with underscores preserved. long_running_task becomes MCP_TIMEOUT_DEMO_TIMEOUT_MS__LONG_RUNNING_TASK (note the double underscore between prefix and tool name). Print env_key_for(tool_name) from the mcp_timeout_demo.config module if you are unsure.

"The tool default advertised in tools/list is wrong"

The advertised default is captured at server startup. If you change the env var or the config file, restart the MCP server (in Claude Code: /mcp → restart the server, or just restart the client).

"I get FileNotFoundError: config file not found"

MCP_TIMEOUT_DEMO_CONFIG must point at an existing file; a missing path is treated as operator error, not silently ignored. Check the path and the process's working directory.

"I get ValueError: timeout ... outside [1, 600000]"

Timeout values are clamped to [1, 600_000] ms (10 minutes). A malformed override fails loudly at startup rather than silently degrading — fix the value in your env or config file.

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Upgrade notes

• Semantic Versioning applies. Minor releases may add tools or config keys; patch releases are strictly bug fixes.
• The env-var prefix (MCP_TIMEOUT_DEMO_) and key template (MCP_TIMEOUT_DEMO_TIMEOUT_MS__<TOOL_NAME_UPPER>) are part of the public API. They will not change inside a major version.
• The JSON config file schema (tools.<name>.timeout_ms) is also part of the public API for the current major.

See CHANGELOG.md for the full release history.

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Development

uv sync
uv run pytest -v

The suite drives the server through the SDK's in-memory transport, so no subprocess or stdio hand-off is required to run it.

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License

MIT — see LICENSE.