Curating tools

A hosted server exposes a curated selection of the tool definitions in the project’s active deployment. Curating covers two tasks: choosing which tools the server exposes, and editing each tool’s metadata so an LLM picks and uses it correctly. For guidance on scoping a server to a task, see Choosing which tools a server exposes.

Curation applies to hosted servers only. Remote and tunneled servers list their tools live and use recorded tool metadata instead. See Tool discovery.

Access requirements

Curating a server’s tools and editing tool variations require the mcp:write scope. The default Admin role holds it and the Member role does not.

Choose the tools a server exposes

Open the server from MCP Gateway > MCP and select its Tools tab. Remove tools that agents do not need, or click Add Tools to add tools from any of the project’s sources. The same tab lists the resources and prompts the server serves.

Tools can also be added or removed from the Playground through Manage tools.

Edit a tool

Endpoints in an OpenAPI document often lack summaries and descriptions that convey their intent. When a tool definition inherits a vague or incomplete description, an LLM may struggle to decide when to call the tool, how to use it, or how to interpret its output. Improving tool metadata is a form of prompt engineering and a critical step in building reliable agents.

There are two ways to improve a tool’s metadata:

Edit the OpenAPI document and add the x-gram extension to the endpoint to override or enrich the tool’s metadata. See Optimize the document for LLMs.
Edit the tool directly in the dashboard. An edit made this way is called a tool variation.

A tool variation overrides a tool’s metadata without changing the underlying source. Beyond the name and description, a variation can override the tool’s tags, its MCP annotations (the title and the read-only, destructive, idempotent, and open-world hints), and its confirmation prompt.

Variations made in the dashboard are global. They apply to the tool everywhere it is used, across every MCP server.

Edit a tool from the Tools tab of a hosted server, or from the Tools tab of a source’s detail page, which opens from the Sources tab of the MCP page (see Sources). Each tool has an actions menu behind its three-dot button.

Rename a tool

Open the actions menu, select Edit name, and update the name in the dialog that opens.

Change a description

Open the actions menu and select Edit description. Validate and save the new description in the dialog:

Edit annotations and tags

The same menu holds Edit annotations and Edit tags for tools generated from OpenAPI documents and functions. Tags set here drive tag-based tool filtering.

Tool kinds and URNs

Every tool definition is identified by a URN in the format tools:<kind>:<source>:<name>. The kind reflects how the tool executes:

http: generated from an OpenAPI operation and executed as an HTTP request to the API
function: backed by a function
externalmcp: proxied to a third-party MCP server added from the catalog or registered by URL
tunneledmcp: proxied to a private MCP server connected through a tunnel
prompt: a prompt template exposed as a tool
platform: a built-in platform tool

Tool URNs appear in the API and SDK when selecting the tools a server exposes. Renaming an operation ID changes the URN, so tool variations keyed to the old URN stop applying. See How a change propagates.