feat: add optional tools allowlist via MCP_TOOLS_INCLUDED

When MCP_TOOLS_INCLUDED is set to a comma-separated list of tool names,
only those tools are exposed (tools/list and calls); unset or empty
exposes every generated tool. Unknown names are ignored with a startup
warning and the active selection is logged at startup.

README.md

@@ -82,6 +82,7 @@ OPENAPI_SPEC_URL=https://petstore3.swagger.io/api/v3/openapi.json uv run xmcp
 | `MCP_HOST` | no | `0.0.0.0` | Listen host for the HTTP transport |
 | `MCP_PORT` | no | `8000` | Listen port for the HTTP transport |
 | `MCP_SERVER_NAME` | no | spec `info.title` | Name advertised by the MCP server |
+| `MCP_TOOLS_INCLUDED` | no | – (all tools) | Comma-separated allowlist of tool names to expose |
 | `HTTP_TIMEOUT` | no | `30` | Timeout in seconds for spec fetch and API calls |
 | `LOG_LEVEL` | no | `INFO` | Python log level |
 
@@ -116,6 +117,20 @@ API request, except credential headers such as `Authorization` and `Cookie`.
 MCP clients that support custom transport headers should send the key on every
 request (at least on `tools/call`).
 
+### Tool allowlist
+
+By default every operation in the OpenAPI document is exposed as an MCP tool.
+Set `MCP_TOOLS_INCLUDED` to a comma-separated list of tool names to expose
+only those:
+
+```sh
+MCP_TOOLS_INCLUDED=getPetById,findPetsByStatus
+```
+
+Unset or empty exposes all tools. Names that do not match a generated tool are
+ignored with a startup warning, and the active selection is reported at startup
+(`Tools allowlist active: exposing N of M tool(s): ...`).
+
 ### Serving a local spec file
 
 ```sh