Add remote MCP server for AI-assisted access to tracker data

[matthelm]

Summary

This adds a Model Context Protocol (MCP) server so AI assistants can query Build Canada tracker data directly. Anyone using Claude Desktop, Claude Code, Cursor, or any MCP client can connect with a single URL:

https://www.buildcanada.com/mcp

In Claude Desktop: Settings → Connectors → Add custom connector → paste the URL.

What's included

12 read-only tools that mirror the existing REST API — no duplicated query logic. Each tool dispatches internally to the existing controllers via Rack, so when a controller or view changes, the MCP output updates automatically.

Tool	REST endpoint	What it does
list_commitments	GET /commitments	Search/filter commitments with pagination
get_commitment	GET /commitments/:id	Full commitment detail with criteria, sources, timeline
list_promises	GET /promises	All platform promises with progress scores
get_promise	GET /promises/:id	Promise detail with evidence links
list_bills	GET /bills	Parliamentary bills with stage dates
get_bill	GET /bills/:id	Bill detail with Parliament API data
list_departments	GET /departments	Departments with minister info
get_department	GET /departments/:id	Department detail with lead promises
list_ministers	GET /ministers	Cabinet officials by portfolio
list_activity	GET /feed	Chronological activity feed
get_commitment_summary	GET /api/dashboard/:id/at_a_glance	Status overview by policy area
get_commitment_progress	GET /api/burndown/:id	Time-series for trend analysis

Implementation

The entire MCP surface is a single controller (mcp_controller.rb) with a declarative config array. Adding a new tool is ~8 lines — just a name, path, description, and schema. The controller dynamically generates MCP::Tool subclasses and dispatches tool calls to existing endpoints via Rack::MockRequest.

Uses the official mcp Ruby SDK (v0.9.1) with stateless Streamable HTTP transport. No session management needed, works on multi-node deploys out of the box.

Testing

29 integration tests covering all 12 tools, filters, not-found paths, and protocol handshake.

To test locally with Claude Desktop:

# Start Rails
bin/rails server -p 3099

# Expose via ngrok
ngrok http 3099

# In Claude Desktop: Settings → Connectors → Add custom connector
# Enter: https://<your-ngrok-url>/mcp

# You may need to allow the ngrok host:
# config/initializers/allow_tunnel.rb (do not commit)
Rails.application.config.hosts.clear

# Run tests
bin/rails test test/controllers/mcp_controller_test.rb

[xrendan]

Can you also update the docs and CLAUDE.md to mention these things.

The mcp server will be available at buildcanada.com/tracker/mcp instead of buildcanada.com/mcp.

[xrendan]

This is really not clear in the code (I need to clean things up), but commitments now replace promises:

list_promises
get_promise

Can you remove these?

[xrendan]

It's slightly more code, but I'd rather this as their own models instead of the dynamic generation.

Can you make this POROs and put them under models/mcp_tools with a concern that has the shared logic here with the properties as methods/class methods on the tool classes directly?

    {
      name: "get_commitment_progress",
      path: "/api/burndown/:government_id",
      description: <<~DESC.strip,
        Commitment progress over time — daily time-series of how many commitments have been
        scoped, started, completed, or broken throughout a government's mandate. Useful for
        trend analysis and charting. Returns { date, scope, started, completed, broken } per
        day, plus mandate_start/end dates. Tracks COMMITMENTS (not promises).
        The government_id for the current Government of Canada is 1.
      DESC
      properties: {
        government_id: { type: "integer", description: "Government ID (1 = current Government of Canada)" },
        source_type: { type: "string", description: "Filter by source type" },
        policy_area_slug: { type: "string", description: "Filter by policy area slug" },
        department_slug: { type: "string", description: "Filter by lead department slug" }
      },
      required: [ "government_id" ]
    }

Becomes something like:

description= <<~DESC.strip,
        Commitment progress over time — daily time-series of how many commitments have been
        scoped, started, completed, or broken throughout a government's mandate. Useful for
        trend analysis and charting. Returns { date, scope, started, completed, broken } per
        day, plus mandate_start/end dates. Tracks COMMITMENTS (not promises).
        The government_id for the current Government of Canada is 1.
      DESC
...