stitch-proxy-ld9

Zero-dependency MCP compatibility proxy for Google Stitch. Normalizes JSON Schema patterns that break Moonshot Kimi and other strict Draft 7 clients.

The problem

Google Stitch MCP emits tool schemas with $ref plus sibling keywords:

{ "$ref": "#/$defs/VariantOptions", "description": "..." }

This is valid in modern JSON Schema, but Kimi/Moonshot rejects it. This proxy rewrites it to:

{ "allOf": [{ "$ref": "#/$defs/VariantOptions" }], "description": "..." }

Quick install

npm install -g stitch-proxy-ld9

Or use without installing:

npx -y stitch-proxy-ld9

Configure OpenCode

Add to ~/.config/opencode/opencode.json:

{
  "mcp": {
    "stitch-proxy-ld9": {
      "type": "local",
      "command": ["stitch-proxy-ld9"],
      "environment": {
        "STITCH_API_KEY": "your-api-key-here"
      }
    }
  }
}

Or using an environment variable (recommended for shared machines):

{
  "mcp": {
    "stitch-proxy-ld9": {
      "type": "local",
      "command": ["stitch-proxy-ld9"],
      "environment": {
        "STITCH_API_KEY": "{env:STITCH_API_KEY}"
      }
    }
  }
}

Then export in your shell profile (.bashrc, .zshrc):

export STITCH_API_KEY="your-api-key-here"

Use

Open OpenCode and verify the MCP is connected:

/mcp

Then prompt:

usa stitch-proxy-ld9 para listar mis proyectos de Stitch

usa stitch-proxy-ld9 para listar las pantallas del proyecto X

usa stitch-proxy-ld9 para obtener el código HTML de la pantalla Y

Auth modes

API key (recommended)

export STITCH_API_KEY="your-api-key"

Access token

export STITCH_ACCESS_TOKEN="your-access-token"
export STITCH_PROJECT_ID="your-google-cloud-project-id"

Optional host override

export STITCH_HOST="https://stitch.googleapis.com/mcp"

Troubleshooting

Symptom	Cause	Fix
Missing Stitch credentials	No API key set	Set STITCH_API_KEY in config or shell
Connection closed in /mcp	OpenCode can't see the key	Verify key is in ~/.config/opencode/opencode.json or exported in shell
tools.function.parameters is not a valid moonshot flavored json schema	Using upstream Stitch directly	Use stitch-proxy-ld9, not stitch
structured content error	Old version	npm install -g stitch-proxy-ld9@latest
command not found: stitch-proxy-ld9	Not installed globally	npm install -g stitch-proxy-ld9

Verify installation

# Check binary exists
which stitch-proxy-ld9

# Run tests (from repo clone)
npm test
npm run typecheck

How it works

OpenCode + Kimi
  → stitch-proxy-ld9 (local stdio MCP)
    → normalizes $ref + siblings → allOf pattern
      → Google Stitch MCP (remote)

• Intercepts tools/list and normalizes every inputSchema
• Forwards tools/call unchanged
• Handles structuredContent for tools with outputSchema
• Uses env-only auth, no secrets logged

Status

Independent compatibility proxy. Not affiliated with Google.

Google Stitch APIs are experimental. Expect changes.

License

MIT