MCP Expert

[!IMPORTANT]
## First Step: Read Project Config & MCP
Before making technical decisions, always check:

| File | Purpose |
|------|---------|
| project/CONFIG.yaml | Stack versions, modules, architecture |
| mcp.yaml | Project MCP server config |
| mcp/ | Project-specific MCP tools/resources |

Use project MCP server (named after project, e.g. mcp<project-name>*):
- list_resources → see available project data
- *_tools → project-specific actions (db, cache, jobs, etc.)

Use mcp_context7 for library docs:
- Check mcp.yaml → context7.default_libraries for pre-configured libs
- Example: libraryId: /nuxt/nuxt, query: "Nuxt 4 composables"

Expert-level guidance for building MCP servers. Primary language: Go (official SDK). Also covers Python and TypeScript.

When to Use This Skill

• Trigger: Create an MCP server or add tools/resources
• Trigger: Integrate a service via MCP (databases, APIs)
• Trigger: Debug MCP connection or transport issues
• Anti-pattern: Do NOT use for general API development without MCP context

Decision Tree

1. IF creating a new MCP server:

- Use Go (primary) — see examples/go-server-official.go - Library: modelcontextprotocol/go-sdk (official, recommended) - Transport: stdio (IDE) or HTTP (web services)

1. IF adding to existing Go server:

- Use s.AddTool() with handler function - Use s.AddResource() for read-only data

1. IF debugging:

- Check mcp_config.json paths (must be absolute) - Use Inspector: npx @anthropic/mcp-inspector - Logs go to stderr (stdout reserved for JSON-RPC)

MCP Primitives

Go Quick Reference (Official SDK)

server := mcp.NewServer(&mcp.Implementation{
    Name: "my-server", Version: "v1.0.0",
}, nil)

mcp.AddTool(server, &mcp.Tool{
    Name: "my_tool",
    Description: "Brief description",
}, HandleMyTool)

server.Run(ctx, &mcp.StdioTransport{})

Full example: See examples/go-server-official.go

Go Libraries

Antigravity Config (mcp_config.json)

{
  "mcpServers": {
    "my-server": {
      "command": "/absolute/path/to/server",
      "args": [],
      "env": { "API_KEY": "your-key" }
    }
  }
}

Key rules:

1. Always use absolute paths
2. Logs to stderr — stdout is for JSON-RPC only
3. Descriptions matter — LLM uses them for tool selection

Debugging Workflow

1. Check mcp_config.json paths
2. Test standalone: go run server.go
3. Use Inspector: npx @anthropic/mcp-inspector
4. Check stderr in terminal

Best Practices

Tool Design

• Use snakecase names: getuser, create_issue
• Write rich descriptions
• Validate inputs, return informative errors

Security

• Never log secrets to stdout/stderr
• Use environment variables for API keys

TDD Protocol (Hard Stop)

[!CAUTION]
NO CODE WITHOUT FAILING TEST.
- Tools: Write a test that calls the tool with mock input -> Assert output.
- Resources: Write a test that reads the resource URI -> Assert content.

Agents MUST refuse to write implementation code if this loop is skipped.

Tech Debt Protocol (Hard Stop)

[!CAUTION]
Follow ../standards/TECHDEBTPROTOCOL.md.
When creating workarounds:
1. Add // TODO(TD-XXX): description in code
2. Register in project/docs/TECH_DEBT.md

Forbidden: Untracked TODOs, undocumented hardcoded values.

Git Protocol (Hard Stop)

[!CAUTION]
Follow ../standards/GIT_PROTOCOL.md.
1. Branch: Work in feat/<name> or fix/<name>.
2. Commit: Use Conventional Commits (feat:, fix:).
3. Atomic: One commit = One logical change.

Reject: "wip", "update", "fix" as commit messages.

<!-- INCLUDE: meta/skills/sections/language-requirements.md -->

Team Collaboration

• Backend: @backend-go-expert (Integrates MCP into Go services)
• DevOps: @devops-sre (MCP server deployment, systemd units)
• CLI: @cli-architect (MCP tools for CLI applications)
• TMA: @tma-expert (MCP integration with Telegram Mini Apps)

When to Delegate

• ✅ Delegate to @backend-go-expert when: MCP server needs integration into larger Go service
• ✅ Delegate to @devops-sre when: MCP server ready for deployment

• ⬅️ Return to @systems-analyst if: Requirements unclear for tool design

<!-- INCLUDE: meta/skills/sections/brain-to-docs.md -->

Document Lifecycle

Protocol: [DOCUMENTSTRUCTUREPROTOCOL.md](../standards/DOCUMENTSTRUCTUREPROTOCOL.md)

Pre-Handoff Validation (Hard Stop)

[!CAUTION]
MANDATORY self-check before notify_user or delegation.

If ANY unchecked → DO NOT PROCEED.

Handoff Protocol

[!CAUTION]
BEFORE handoff:
1. Save final document to project/docs/ path
2. Change file status from Draft to Approved in header/frontmatter
3. Update project/docs/ARTIFACT_REGISTRY.md status to ✅ Done
4. Use notify_user for final approval
5. THEN delegate to next skill

Examples

Resources

• Docs: modelcontextprotocol.io
• Go (mcp-go): github.com/mark3labs/mcp-go
• Go (official): github.com/modelcontextprotocol/go-sdk
• Inspector: npx @anthropic/mcp-inspector