Forge MCP Server

forge-mcp

Author, compile, run, and commit generative-music E-- Recipes directly from any MCP-capable agent (Claude Desktop, Cursor, …). forge-mcp exposes the Forge E-- library note catalog + vault as an MCP server and closes the authoring loop end-to-end: the agent picks a chip from the catalog, drafts a Recipe, verifies it parses, runs it in a sandbox, previews the artifact, and commits the finished Recipe to a vault note. All 6 tools ship today.

[library note catalog] → [compile] → [run] → [commit] → [vault note with recipe_version bump]

Install into Claude Code

Fastest path — Claude Code spawns forge-mcp as a stdio subprocess. Full walkthrough at docs/claude-code-install.md.

# 1. Install from PyPI (https://pypi.org/project/forge-recipe-mcp/)
pip install forge-recipe-mcp

# 2. Fetch your Bearer once and export
export FORGE_MCP_BEARER=$(jq -r '.transpileServiceToken' \
  ~/forge-vaults/bluh/.obsidian/plugins/forge-client-obsidian/data.json)

# 3. Register with Claude Code
claude mcp add forge-mcp \
  -e FORGE_MCP_BEARER=$FORGE_MCP_BEARER \
  -e FORGE_TRANSPILE_URL=https://forge.thecodingarena.com \
  -e FORGE_VAULT_PATH=$HOME/forge-vaults/bluh \
  -e FORGE_MCP_TRANSPORT=stdio \
  -- forge-mcp

# 4. Start Claude Code and ask "list the notes in my forge music library."

Install (other clients)

Full walkthrough (Claude Desktop config, forge-transpile Bearer acquisition, verification smoke, troubleshooting): docs/install.md.

Quick paths:

# From source (pip + editable install for development)
pip install -e ".[dev]"
python -m forge_mcp.server

# Docker
docker build -t forge-mcp:latest .
docker run --rm -p 8765:8765 \
    -e FORGE_TRANSPILE_URL=https://forge.thecodingarena.com \
    -e FORGE_VAULT_PATH=/path/to/your/vault \
    forge-mcp:latest

Environment:

• FORGE_TRANSPILE_URL — base URL of the forge-transpile service. Default: http://localhost:8000.
• FORGE_VAULT_PATH — local vault directory for forge_read_notes_in_vault + forge_commit_recipe. Default: ~/forge-vaults/bluh.
• FORGE_MCP_HOST — host to bind. Default: 0.0.0.0.
• FORGE_MCP_PORT — port to bind. Default: 8765.
• FORGE_MCP_BEARER — dev fallback only. Per-request Bearer extraction is the primary path (CW-MCP-1-B); this env var only fires when the incoming request has no Authorization header. Do NOT set in production.

Claude Desktop config

Add to ~/Library/Application Support/Claude/claude_desktop_config.json:

{
  "mcpServers": {
    "forge-mcp": {
      "url": "http://localhost:8765/mcp",
      "headers": {
        "Authorization": "Bearer <your-forge-transpile-token>"
      }
    }
  }
}

Get your Bearer:

jq -r '.transpileServiceToken' \
    ~/forge-vaults/bluh/.obsidian/plugins/forge-client-obsidian/data.json

Tools

Read (no side effects):

• forge_read_note_catalog({domain?}) — list Forge library notes; every entry carries the E-- signature the agent needs to Call it.
• forge_read_notes_in_vault({filter?}) — list vault notes with a has_recipe + recipe_version summary. Backed by a local filesystem walk (CW-MCP-2-E).

Author (deterministic — no LLM, no vault write):

• forge_compile_recipe({source}) — Recipe → Python. Returns compiled source + unresolved slot count, OR a structured parse error with line/column (per drain CW-recipe-parser-line-info).
• forge_run_recipe({source, domains?}) — compile + execute in a resource-limited server sandbox. Returns a short preview + a run_id; artifacts (MusicXML / MIDI / PNGs) accessible via the forge-artifact:// resource.
• forge_get_run_result({run_id}) — fetch full stdout/stderr + artifact manifest of a previous run. 7-day TTL, per-Bearer isolation.

Commit:

• forge_commit_recipe({source, note_id, expected_version?}) — persist Recipe to a vault note (facet-scoped — Description + Python + frontmatter survive byte-for-byte). Bumps recipe_version in the note's frontmatter. Optimistic-concurrency via expected_version; version-conflict returns isError:true with expected + current numbers.

Resources

• forge-note:///{domain}/{name} — library note content.
• forge-artifact:///{run_id}/{artifact_name} — on-demand binary fetch for run artifacts. Text mimes return via text; binaries via base64 blob.
• forge-recipe:///{note_id}/v{n} — Recipe body at a specific recipe_version (git-tracked vaults only; returns "history unavailable" text otherwise).

Auth

forge-mcp does NOT validate tokens itself — forge-transpile is the source of truth (guarded by FORGE_TRANSPILE_SECRET). Each request's Authorization: Bearer <token> header is forwarded verbatim; a 401 or 403 from forge-transpile surfaces as isError: true with an actionable message the agent can read (drain CW-MCP-1-B).

Rotation is zero-downtime on the forge-mcp side: change FORGE_TRANSPILE_SECRET on forge-transpile, update your MCP client's header, done. Old tokens fail on the next request with a clean rejection message.

Related repos

• forge — the E-- parser + transpiler + core music library. forge-mcp vendors a snapshot of forge/recipe/ per the CW-MCP-2-A architecture; drift is caught by scripts/check-recipe-drift.sh in the forge-transpile repo.
• forge-transpile — the FastAPI service exposing /compile / /run / /catalog etc. that forge-mcp's tools proxy for the transpile + sandboxed-run paths. Vault reads + commits are LOCAL and don't hit forge-transpile.
• forge-client-obsidian — the Obsidian plugin end of the same authoring loop. forge-mcp writes to the SAME vault the plugin reads/renders; both share the note-file format.