# Call a tool

> Directly invokes a tool and returns its output. Supported for `http`, `builtin`, `mcp`, and `pipeline` tools. `client` tools cannot be invoked server-side and will return 422. A `pipeline` tool runs its declared steps in order and returns the mapped `output` (or the last step's output); `action` is ignored and `input` is the pipeline input.

<Heading
  as={"h1"}
  className={"openapi__heading"}
  children={"Call a tool"}
>
</Heading>

<MethodEndpoint
  method={"post"}
  path={"/api/v1/tools/{tool_id}/call"}
  context={"endpoint"}
>
  
</MethodEndpoint>

Directly invokes a tool and returns its output. Supported for `http`, `builtin`, `mcp`, and `pipeline` tools. `client` tools cannot be invoked server-side and will return 422. A `pipeline` tool runs its declared steps in order and returns the mapped `output` (or the last step's output); `action` is ignored and `input` is the pipeline input.
For `builtin` and `mcp` tools the `action` field is required and identifies which action (SOAT) or tool name (MCP) to invoke. For `http` tools `action` is ignored. When a `builtin` or `mcp` tool declares an `actions` allowlist, an action outside it is rejected with `400 VALIDATION_FAILED` ("not available on this tool") before any outbound request is made.
`preset_parameters` stored on the tool are pinned over the caller-supplied `input` before execution: a key the tool presets keeps its preset value even when `input` sets it. Keys the presets do not name are taken from `input` as sent.
Guardrails attached to the tool or to its project adjudicate the call before dispatch, composing project + tool scope. A call this route cannot await a decision on — class C (human sign-off), class D, or a class-B tripwire — is refused with `422 TOOL_DISPATCH_FAILED`, whose `meta` carries the `tool_id` and the `outcome`. A `pipeline` tool is adjudicated before its first step runs, and every step is adjudicated as the call of that tool it is.

<Heading
  id={"request"}
  as={"h2"}
  className={"openapi-tabs__heading"}
>
  <Translate id="theme.openapi.request.title">Request</Translate>
</Heading>

<ParamsDetails
  {...require("./call-tool.ParamsDetails.json")}
>
  
</ParamsDetails>

<RequestSchema
  {...require("./call-tool.RequestSchema.json")}
>
  
</RequestSchema>

<StatusCodes
  {...require("./call-tool.StatusCodes.json")}
>
  
</StatusCodes>