MCP expose tools

When to use this

You want AI agents to call your business logic through the Model Context Protocol (MCP) without writing a separate API layer.

MCP is a protocol, not a programming model: stateless JSON-RPC tool calls only — no object lifetimes, callbacks, or rich sessions. Graftcode projects existing static methods as MCP tools via Gateway configuration. The same facade can serve Grafts, edge clients, and AI tools. Method comments become MCP tool descriptions. Stateful workflows stay on Grafts, not MCP.

Hands-on: Quick Start #5

MCP exposure topology — static methods through Gateway to MCP clients and Grafts

Prerequisites

Public static methods on an exposed class (MCP is stateless request–response)
Ports and CORS configured for browser-based MCP clients

Steps

1. Design an MCP-friendly facade

Use a class with public static methods and XML/doc comments (they become tool descriptions):

public static class AiToolsFacade
{
    /// <summary>Returns the current price for a region code.</summary>
    public static decimal GetPrice(string region) => /* ... */;
}

2. Start GG with MCP base class

./gg ./MyLib.dll \
  --types MyCompany.AiToolsFacade \
  --mcpBaseClass MyCompany.AiToolsFacade \
  --port 8888 \
  --httpPort 8889 \
  --corsConfig ./cors.config

--mcpBaseClass is the fully qualified type name used when tools/call receives a bare method name without params.class.

3. MCP HTTP endpoints

Served on the HTTP port (--httpPort):

Endpoint	Method	Purpose
`/mcp`	GET, POST, DELETE, OPTIONS	MCP JSON-RPC session
`/mcpmodel`	GET	MCP tool schema from UGM
`/mcpport`	GET	Returns WebSocket port (same as `--port`) for MCP clients

Example:

curl http://localhost:8889/mcpport
curl http://localhost:8889/mcpmodel

WebSocket MCP traffic uses --port (default 80; use 8888 in dev).

5. Connect an MCP client

On the Vision Installation tab, open Connect and select MCP. Vision generates the client configuration for your Gateway:

Graftcode Vision Connect tab showing MCP client JSON with the Gateway MCP endpoint URL

Copy this JSON into your MCP host — for example Cursor's MCP settings or .cursor/mcp.json. Adjust the URL if your Gateway uses a non-default HTTP port (e.g. http://localhost:81/mcp).

For Cursor, you can also add the server under Settings → Tools & MCP. Claude Desktop may require mcp-remote for HTTP endpoints — see Quick Start #5.

6. CORS for MCP clients

Include MCP headers in CORS config:

allowedOrigins=http://localhost:3000
allowedHeaders=content-type,authorization,MCP-Protocol-Version,Mcp-Session-Id
exposedHeaders=Mcp-Session-Id,MCP-Protocol-Version

Verify it works

/mcpmodel returns tool definitions matching your static methods
MCP client lists tools and successfully calls GetPrice
Method comments appear as tool descriptions

Common mistakes

Mistake	Fix
Instance methods only	MCP exposes static methods; add a static facade
CORS blocks browser MCP	Add MCP headers to `--corsConfig`
Wrong `--mcpBaseClass` FQN	Must match UGM type name exactly
Stateful workflows via MCP	Use Grafts for stateful; MCP stays stateless