/discourse-mcp

MCP client for Discourse sites

Primary LanguageTypeScriptMIT LicenseMIT

Discourse MCP

A Model Context Protocol (MCP) stdio server that exposes Discourse forum capabilities as tools for AI agents.

  • Entry point: src/index.ts → compiled to dist/index.js (binary name: discourse-mcp)
  • SDK: @modelcontextprotocol/sdk
  • Node: >= 18

Quick start (release)

  • Run (read‑only, recommended to start)
npx -y @discourse/mcp@latest

Then, in your MCP client, either:

  • Call the discourse_select_site tool with { "site": "https://try.discourse.org" } to choose a site, or

  • Start the server tethered to a site using --site https://try.discourse.org (in which case discourse_select_site is hidden).

  • Enable writes (opt‑in, safe‑guarded)

npx -y @discourse/mcp@latest --allow_writes --read_only=false --auth_pairs '[{"site":"https://try.discourse.org","api_key":"'$DISCOURSE_API_KEY'","api_username":"system"}]'
  • Use in an MCP client (example: Claude Desktop) — via npx
{
  "mcpServers": {
    "discourse": {
      "command": "npx",
      "args": ["-y", "@discourse/mcp@latest"],
      "env": {}
    }
  }
}

Alternative: if you prefer a global binary after install, the package exposes discourse-mcp.

{
  "mcpServers": {
    "discourse": { "command": "discourse-mcp", "args": [] }
  }
}

Configuration

The server registers tools under the MCP server name @discourse/mcp. Choose a target Discourse site either by:

  • Using the discourse_select_site tool at runtime (validates via /about.json), or

  • Supplying --site <url> to tether the server to a single site at startup (validates via /about.json and hides discourse_select_site).

  • Auth

    • None by default.
    • --auth_pairs '[{"site":"https://example.com","api_key":"...","api_username":"system"}]': Per‑site API key overrides. You can include multiple entries; the matching entry is used for the selected site.

  • Write safety

    • Writes are disabled by default.
    • The tool discourse.create_post is only registered when all are true:
      • --allow_writes AND not --read_only AND some auth is configured (either default flags or a matching auth_pairs entry).
    • A ~1 req/sec rate limit is enforced for create_post.

  • Flags & defaults

    • --read_only (default: true)
    • --allow_writes (default: false)
    • --timeout_ms <number> (default: 15000)
    • --concurrency <number> (default: 4)
    • --log_level <silent|error|info|debug> (default: info)
    • --tools_mode <auto|discourse_api_only|tool_exec_api> (default: auto)
    • --site <url>: Tether MCP to a single site and hide discourse_select_site.
    • --default-search <prefix>: Unconditionally prefix every search query (e.g., tag:ai order:latest-post).
    • --max-read-length <number>: Maximum characters returned for post content (default 50000). Applies to discourse_read_post and per-post content in discourse_read_topic. The tools prefer raw content by requesting include_raw=true.
    • --cache_dir <path> (reserved)
    • --profile <path.json> (see below)

  • Profile file (keep secrets off the command line)

{
  "auth_pairs": [
    { "site": "https://try.discourse.org", "api_key": "<redacted>", "api_username": "system" }
  ],
  "read_only": false,
  "allow_writes": true,
  "log_level": "info",
  "tools_mode": "auto",
  "site": "https://try.discourse.org"
  ,
  "default_search": "tag:ai order:latest-post"
  ,
  "max_read_length": 50000
}

Run with:

node dist/index.js --profile /absolute/path/to/profile.json

Flags still override values from the profile.

  • Remote Tool Execution API (optional)

    • With tools_mode=auto (default) or tool_exec_api, the server discovers remote tools via GET /ai/tools after you select a site (or immediately at startup if --site is provided) and registers them dynamically. Set --tools_mode=discourse_api_only to disable remote tool discovery.

  • Networking & resilience

    • Retries on 429/5xx with backoff (3 attempts).
    • Lightweight in‑memory GET cache for selected endpoints.

  • Privacy

    • Secrets are redacted in logs. Errors are returned as human‑readable messages to MCP clients.

Tools

Built‑in tools (always present unless noted):

  • discourse_search
    • Input: { query: string; with_private?: boolean; max_results?: number (1–50, default 10) }
    • Output: text summary plus a compact footer like: 
      { "results": [{ "id": 123, "url": "https://…", "title": "…" }] }
  • discourse_read_topic
    • Input: { topic_id: number; post_limit?: number (1–20, default 5) }
  • discourse_read_post
    • Input: { post_id: number }
  • discourse_list_categories
    • Input: {}
  • discourse_list_tags
    • Input: {}
  • discourse_get_user
    • Input: { username: string }
  • discourse_filter_topics
    • Input: { filter: string; page?: number (default 1); per_page?: number (1–50) }
    • Query language (succinct): key:value tokens separated by spaces; category/categories (comma = OR, =category = without subcats, - prefix = exclude); tag/tags (comma = OR, + = AND) and tag_group; status:(open|closed|archived|listed|unlisted|public); personal in: (bookmarked|watching|tracking|muted|pinned); dates: created/activity/latest-post-(before|after) with YYYY-MM-DD or relative days N; numeric: likes[-op]-(min|max), posts-(min|max), posters-(min|max), views-(min|max); order: activity|created|latest-post|likes|likes-op|posters|title|views|category with optional -asc; free text terms are matched.
  • discourse_create_post (only when writes enabled; see Write safety)
    • Input: { topic_id: number; raw: string (≤ 30k chars) }

Notes:

  • Outputs are human‑readable first. Where applicable, a compact JSON is embedded in fenced code blocks to ease structured extraction by agents.

Development

  • Requirements: Node >= 18, pnpm.

  • Install / Build / Typecheck / Test

pnpm install
pnpm typecheck
pnpm build
pnpm test
  • Run locally (with source maps)
pnpm build && pnpm dev

  • Project layout

    • Server & CLI: src/index.ts
    • HTTP client: src/http/client.ts
    • Tool registry: src/tools/registry.ts
    • Built‑in tools: src/tools/builtin/*
    • Remote tools: src/tools/remote/tool_exec_api.ts
    • Logging/redaction: src/util/logger.ts, src/util/redact.ts

  • Testing notes

    • Tests run with Node’s test runner against compiled artifacts (dist/test/**/*.js). Ensure pnpm build before pnpm test if invoking scripts individually.

  • Publishing (optional)

    • The package is published as @discourse/mcp and exposes a bin named discourse-mcp. Prefer npx @discourse/mcp@latest for frictionless usage.

  • Conventions

    • Focus on text‑oriented outputs; keep embedded JSON concise.
    • Be careful with write operations; keep them opt‑in and rate‑limited.

See AGENTS.md for additional guidance on using this server from agent frameworks.

Examples

  • Read‑only session against try.discourse.org:
npx -y @discourse/mcp@latest --log_level debug
# In client: call discourse_select_site with {"site":"https://try.discourse.org"}
  • Tether to a single site:
npx -y @discourse/mcp@latest --site https://try.discourse.org
  • Create a post (writes enabled):
npx -y @discourse/mcp@latest --allow_writes --read_only=false --auth_pairs '[{"site":"https://try.discourse.org","api_key":"'$DISCOURSE_API_KEY'","api_username":"system"}]'

FAQ

  • Why is create_post missing? You’re in read‑only mode. Enable writes as described above.
  • Can I disable remote tool discovery? Yes, run with --tools_mode=discourse_api_only.
  • Can I avoid exposing discourse_select_site? Yes, start with --site <url> to tether to a single site.
  • Time outs or rate limits? Increase --timeout_ms, and note built‑in retry/backoff on 429/5xx.