Contributing Skill for Claude

1. Overview

Contributor guide for the Butterbase monorepo. Covers architecture, how to add MCP tools, API routes, database migrations, and coding conventions.

2. Monorepo Map

| Directory | Package | Purpose |

|-----------|---------|---------|

| packages/cli | @butterbase/cli (v0.1.3) | Published CLI tool (Commander.js). Commands: init, apps, schema, functions, storage, deploy, data, env, keys, realtime, status, open |

| packages/sdk | @butterbase/sdk (v1.2.1) | Published TypeScript SDK. Modules: auth, storage, functions, AI, billing, realtime, admin |

| packages/shared | @butterbase/shared | Internal shared types, constants, schema DSL, error types |

| packages/plugin | @butterbase/plugin | Claude Code plugin (this package — skills for AI agents) |

| services/control-api | @butterbase/control-api | Fastify API server — the brain. Routes, plugins, services. Port 4000 |

| services/mcp-server | @butterbase/mcp-server | MCP server with ~28 tools (consolidated manage_* action-based tools + a few standalone ones like init_app, deploy_function, select_rows). Runs via stdio or HTTP (served by control-api at /mcp) |

| services/deno-runtime | — | Serverless function executor. Deno-based worker isolation. Port 7133 |

| services/cron-scheduler | @butterbase/cron-scheduler | Cron job runner using node-cron + cron-parser |

| services/dashboard | — | React management UI (Vite + Radix UI) |

| services/dashboard-api | — | Dashboard backend proxy. Port 4100 |

| services/docs | @butterbase/docs | Astro/Starlight documentation site |

| services/storage-indexer | — | Cloudflare Worker for S3 event indexing |

| db/control-plane | — | SQL migrations (sequential numbering, 001_ upward). Control plane database schema |

| db/data-plane | — | Per-app database initialization scripts |

3. Adding a New MCP Tool (4 Steps)

Step 1: Create tool file at services/mcp-server/src/tools/my-new-tool.ts

Decide whether the new capability is a standalone tool (single, self-contained operation like init_app) or another action on an existing umbrella tool (manage_schema, manage_function, etc). Most new operations should be added as actions on an existing manage_* tool — this keeps the surface area small for AI agents.

For a brand-new standalone tool, follow the pattern from init-app.ts:

import type { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';
import { z } from 'zod';
import { apiPost } from '../api-client.js';

interface MyResponse {
  // response shape
}

export function registerMyNewTool(server: McpServer) {
  server.tool(
    'my_new_tool',      // snake_case name
    `Tool description.   // Multi-line description with examples

Example:
  Input: { ... }
  Output: { ... }

Common errors:
  - ERROR_CODE: Description`,
    {
      // Zod schema for parameters
      app_id: z.string().describe('The app ID'),
      param: z.string().describe('Parameter description'),
    },
    async ({ app_id, param }) => {
      const result = await apiPost<MyResponse>(`/v1/${app_id}/my-endpoint`, { param });
      return {
        content: [{
          type: 'text' as const,
          text: JSON.stringify(result, null, 2),
        }],
      };
    }
  );
}

API client functions available: apiGet, apiPost, apiPatch, apiDelete (from ../api-client.js).

Step 2: Register in services/mcp-server/src/create-server.ts

import { registerMyNewTool } from './tools/my-new-tool.js';
// ...
registerMyNewTool(server);

Step 3: Create the backing API route in services/control-api/src/routes/

• Fastify route handler matching the endpoint your tool calls
• Register in services/control-api/src/index.ts

Step 4: Update documentation in services/mcp-server/src/docs/user-documentation.ts

• Add tool to the relevant section's table in the SECTIONS object

4. Adding a Database Migration

• IMPORTANT: Use scripts/migrate.ts or scripts/backfill-migrations.ts, NEVER raw psql
• Migration files: db/control-plane/NNN_description.sql (sequential numbering, starting at 001_initial_schema.sql)
• Pick the next free three-digit prefix; never edit a committed migration
• Run migrations: npx tsx scripts/migrate.ts

5. Coding Conventions

| Convention | Example |

|-----------|---------|

| MCP tool names | snake_case. Two flavours: standalone (init_app, deploy_function, select_rows) and manage_* umbrella tools that take an action enum (manage_schema, manage_rls, manage_function, manage_frontend, etc.) |

| App IDs | app_ prefix: app_abc123 |

| Service keys | bb_sk_ prefix: bb_sk_a1b2c3... |

| Environment variables | BUTTERBASE_ prefix: BUTTERBASE_API_KEY |

| Response metadata | _meta.next_actions (suggested next tool calls), _meta.resource_info (quota/state) |

| Error codes | UPPERCASE_WITH_UNDERSCORES: AUTH_RLS_POLICY_VIOLATION, QUOTA_TABLE_LIMIT |

| Domain | butterbase.ai (never "nira") |

6. Running Locally

docker-compose -f docker-compose.local.yml up

| Service | Port | URL |

|---------|------|-----|

| Control API | 4000 | http://localhost:4000 |

| Dashboard API | 4100 | http://localhost:4100 |

| Deno Runtime | 7133 | http://localhost:7133 |

| Control Plane DB | 5433 | postgres://localhost:5433 |

| Data Plane DB | 5435 | postgres://localhost:5435 |

| PgBouncer | 6432 | postgres://localhost:6432 |

| LocalStack (S3) | 4566 | http://localhost:4566 |

7. Testing

• Framework: Vitest
• Run tests per workspace: cd services/control-api && npm test
• Test files: __tests__/ directory or co-located *.test.ts
• Build all workspaces: npm run build (from repo root)
• Type check: npx tsc --noEmit in each workspace