io.github.cyanheads/stackexchange-mcp-server

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Overview

Stack Exchange network access — Stack Overflow, Super User, Server Fault, Unix & Linux, and the wider network. Search questions, fetch complete Q&A threads as clean markdown, browse tag FAQs, and look up user profiles from any MCP client. Runs as a stdio process, a local Streamable HTTP server, or the public hosted endpoint above.

Tools

Tool	Description
stackexchange_search_questions	Search questions across a Stack Exchange site with full-text query, tag filters, score threshold, and sort order
stackexchange_get_thread	Fetch a question and its answers as markdown, with a configurable answer limit and the accepted answer first
stackexchange_get_tag_faq	Fetch the highest-voted answered questions for a tag — the canonical "best answers in X" list
stackexchange_get_user	Fetch a user profile by ID: reputation, badge counts, top tags by answer score, and account metadata
stackexchange_list_sites	Enumerate all Stack Exchange network sites and their api_site_parameter values

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Capability reference

stackexchange_search_questions _tool

• Full-text query with optional tag filters, minimum score threshold, and accepted-only filter; sort by relevance (default), votes, activity, or newest
• Up to 30 results per page (default 10); page for more — each page costs one API quota unit, and paging past 25 requires STACKEXCHANGE_API_KEY
• Returns question ID, title, score, answer count, tags, and a ~300-character excerpt — IDs flow directly into stackexchange_get_thread
• Quota remaining and max surfaced via enrichment on every response

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stackexchange_get_thread _tool

• Accepts a numeric question ID or a full Stack Exchange question URL; fetches the question and a page of maxAnswers answers (1–100, default 10), adding the accepted answer if it falls outside that page
• HTML→markdown normalization built in — code blocks, links, lists, headers, and blockquotes all converted
• Optional includeComments fetches up to 20 comments per post, newest first, using two extra API calls (one when there are no answers); commentsTruncated reports partial lists
• Attribution (author name, profile link, score) on every answer per CC BY-SA 4.0
• Quota remaining and max surfaced via enrichment; truncated when more answers exist upstream than maxAnswers returned

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stackexchange_get_tag_faq _tool

• Highest-voted answered questions for a tag — maps to /tags/{tag}/faq, the canonical "best answers in X" list
• Up to 30 results per page (default 10); page for more — each page costs one API quota unit, and paging past 25 requires STACKEXCHANGE_API_KEY
• Returns a question list without bodies; pipe any questionId into stackexchange_get_thread for full content
• Quota remaining and max surfaced via enrichment on every response

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stackexchange_get_user _tool

• userId must be at most 2,147,483,647 (32-bit) — typically the authorUserId from stackexchange_get_thread output
• Fetches the profile and top tags in two upstream API calls
• Returns reputation, badge counts (gold/silver/bronze), location, website, answer/question counts, and up to 10 top tags by answer score (empty array for users with no answers)
• An unknown user ID returns a typed user_not_found error — Stack Exchange answers HTTP 200 with empty results rather than 404

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stackexchange_list_sites _tool

• Fetches every site in the Stack Exchange network, walking pages of 100 up to a 10-page cap; an enrichment notice flags a partial list if the network still has more
• Optional case-insensitive name filter matches against site name and api_site_parameter, applied client-side after the fetch
• Returns the api_site_parameter value (e.g. stackoverflow, superuser, serverfault) that every other tool's site parameter accepts

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Features

Built on @cyanheads/mcp-ts-core: stdio and Streamable HTTP transports, pluggable auth (none / jwt / oauth), swappable storage (in-memory, filesystem, Supabase, Cloudflare KV/R2/D1), structured logging with optional OpenTelemetry tracing.

Stack Exchange-specific:

• HTML→markdown conversion preserves code blocks, tables, links, images, and nested lists
• Shared upstream queue honors response backoff and HTTP 429 cooldowns; each operation has a 50-second budget covering queue time, backoff, requests, and retries
• Quota logging: quota_remaining and quota_max surfaced via enrichment on every tool call
• Typed error contracts on every tool — invalid_site, invalid_parameter, invalid_api_key, invalid_id_or_url, invalid_user_id, question_not_found, user_not_found, paging_depth_limit, quota_exceeded, and upstream_unavailable
• Optional STACKEXCHANGE_API_KEY lifts the per-IP quota from ~300/day to ~10,000/day with no OAuth required

Agent-friendly output:

• Quota remaining on every response — agents can plan around rate limits without the server needing to fail
• The accepted answer appears first, followed by the remaining answers sorted by score
• Each answer includes attribution under CC BY-SA 4.0
• Typed not_found errors for missing questions and users (SE returns HTTP 200 with empty items[] rather than 404)

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Getting started

Public Hosted Instance

A public instance is available at https://stackexchange.caseyjhand.com/mcp — no installation required. Point any MCP client at it via Streamable HTTP:

{
  "mcpServers": {
    "stackexchange-mcp-server": {
      "type": "streamable-http",
      "url": "https://stackexchange.caseyjhand.com/mcp"
    }
  }
}

Self-Hosted / Local

Add the following to your MCP client configuration file.

{
  "mcpServers": {
    "stackexchange": {
      "type": "stdio",
      "command": "bunx",
      "args": ["@cyanheads/stackexchange-mcp-server@latest"],
      "env": {
        "MCP_TRANSPORT_TYPE": "stdio",
        "MCP_LOG_LEVEL": "info"
      }
    }
  }
}

Or with npx (no Bun required):

{
  "mcpServers": {
    "stackexchange": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "@cyanheads/stackexchange-mcp-server@latest"],
      "env": {
        "MCP_TRANSPORT_TYPE": "stdio",
        "MCP_LOG_LEVEL": "info"
      }
    }
  }
}

Or with Docker:

{
  "mcpServers": {
    "stackexchange": {
      "type": "stdio",
      "command": "docker",
      "args": [
        "run", "-i", "--rm",
        "-e", "MCP_TRANSPORT_TYPE=stdio",
        "ghcr.io/cyanheads/stackexchange-mcp-server:latest"
      ]
    }
  }
}

For Streamable HTTP, set the transport and start the server:

MCP_TRANSPORT_TYPE=http MCP_HTTP_PORT=3010 bun run start:http
# Server listens at http://localhost:3010/mcp

Rate limits: The Stack Exchange API allows ~300 requests/day per IP without a key. Set STACKEXCHANGE_API_KEY in env to lift this to ~10,000/day. Register a key at stackapps.com/apps/oauth/register (the OAuth flow is only required for write access — a key alone is sufficient for read-only use).

Prerequisites

• Bun v1.4.0 or higher (or Node.js v24+)
• A STACKEXCHANGE_API_KEY is optional but strongly recommended for any sustained use

Installation

1. Clone the repository:

git clone https://github.com/cyanheads/stackexchange-mcp-server.git

2. Navigate into the directory:

cd stackexchange-mcp-server

3. Install dependencies:

bun install

4. Configure environment:

cp .env.example .env
# edit .env and set STACKEXCHANGE_API_KEY if desired

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Configuration

Variable	Description	Default
STACKEXCHANGE_API_KEY	Optional. Stack Exchange API key — lifts per-IP quota from ~300/day to ~10,000/day.	—
MCP_TRANSPORT_TYPE	Transport: stdio or http.	stdio
MCP_HTTP_PORT	Port for HTTP server.	3010
MCP_HTTP_HOST	Host for HTTP server.	127.0.0.1
MCP_SESSION_MODE	HTTP session mode: auto, stateful, or stateless. auto resolves to stateful. A meaningful env value overrides this server's stateless source default; blank or unsubstituted placeholders use the source default.	stateless
MCP_AUTH_MODE	Auth mode: none, jwt, or oauth.	none
MCP_LOG_LEVEL	Log level (RFC 5424).	info
LOGS_DIR	Directory for log files (Node.js only).	<project-root>/logs
STORAGE_PROVIDER_TYPE	Storage backend.	in-memory
OTEL_ENABLED	Enable OpenTelemetry instrumentation (spans, metrics, completion logs).	false

See .env.example for the full list of optional overrides.

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Running the server

Local development

• Build and run:

  # One-time build
  bun run rebuild
  
  # Run the built server
  bun run start:stdio
  # or
  bun run start:http
  

• Run checks and tests:

  bun run devcheck   # Lint, format, typecheck, security
  bun run test       # Vitest test suite
  bun run lint:mcp   # Validate MCP definitions against spec
  

Docker

docker build -t stackexchange-mcp-server .
docker run --rm -e STACKEXCHANGE_API_KEY=your-key -p 3010:3010 stackexchange-mcp-server

The Dockerfile defaults to HTTP transport, stateless session mode, and logs to /var/log/stackexchange-mcp-server. OpenTelemetry peer dependencies are installed by default — build with --build-arg OTEL_ENABLED=false to omit them.

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Project structure

Path	Purpose
src/index.ts	createApp() entry point — registers tools and inits services.
src/config/	Server-specific environment variable parsing with Zod (STACKEXCHANGE_API_KEY).
src/mcp-server/tools/	Tool definitions (*.tool.ts).
src/services/stackexchange/	Stack Exchange API v2.3 HTTP client, backoff tracking, quota logging, HTML→markdown normalizer.
tests/	Vitest unit and integration tests.
docs/	Design document and directory tree.

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Development guide

See CLAUDE.md/AGENTS.md for development guidelines and architectural rules. The short version:

• Handlers throw, framework catches — no try/catch in tool logic
• Use ctx.log for request-scoped logging, ctx.state for tenant-scoped storage
• Register new tools via the barrel in src/mcp-server/tools/definitions/index.ts
• Wrap external API calls: validate raw → normalize to domain type → return output schema; never fabricate missing fields

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Contributing

Issues are welcome. Run checks and tests before submitting:

bun run devcheck
bun run test

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License

Apache-2.0 — see LICENSE for details.