Reference · Sessions and engines
The MCP tool catalogue
What the MCP tools page shows and what each of its fields means.
Held in Help as its own page, MCP tools lists every tool a server gives the current session. This reaches beyond Claude Code's own built-in ones: this app's own servers, and those a mode connects to. The page reads the running session rather than a written list. What it shows depends on which modes are loaded and which external servers answered.
Server fields
| Field | Meaning |
|---|---|
| Title | The server's own name. |
| Key | The wire name of the server, shown only when it differs from the title. |
| Source | Contributed by a mode, built into the app, or a connected external server. |
| Description | What the server is for. |
| Availability | Which sessions see this server. |
| Endpoint | Shown for an external server, naming where its tools came from. |
A server with no tools names why, in place of an empty list. Sometimes there are none: a mode's own server can carry no tools of its own, and an external server can answer with none. Every other reason is a failure of some kind:
- It is not reached over HTTP, which is the only transport this screen can ask.
- It refused the request.
- It answered in a shape this version does not understand.
- The request itself failed before an answer arrived.
- This build never asked it at all.
Tool fields
| Field | Meaning |
|---|---|
| Name | The tool's own name. |
| Wire name | mcp__<server key>__<tool name>, what the model sees and what a permission rule matches. |
| Loading | Always loaded into every turn's prompt, or found through a tool search. |
| Description | What the tool does, exactly as the model reads it. |
| Parameters | Each argument's name and type, marked optional where the schema allows leaving it out. |
| Search hint | Shown only for a tool found through search: the phrase that search matches. |
A tool taking no arguments says so in place of an empty parameter list. Where the schema describes an argument, that description sits beside it rather than only the name and type.