close

Create Custom Tool

Create a code-backed custom tool in a workspace. Its title must be unique because tools resolve by title at call time.

POST/api/v2/custom-tools

Authorization

apiKey
X-API-Key<token>

Your Sim API key, personal or workspace-scoped. Generate one under Settings, then API Keys. Operations that reject workspace keys say so in their own description.

In: header

Request Body

application/json

Definition and implementation of a new custom tool.

TypeScript Definitions

Use the request body type in TypeScript.

Response Body

application/json

application/json

application/json

application/json

application/json

application/json

application/json

application/json

application/json

application/json

curl -X POST "https://www.sim.ai/api/v2/custom-tools" \  -H "X-API-Key: YOUR_API_KEY" \  -H "Content-Type: application/json" \  -d '{    "workspaceId": "a91c4b2e-6d3f-4e8a-b5c7-0d9e2f1a8c64",    "title": "lookup_order",    "schema": {      "type": "function",      "function": {        "name": "lookup_order",        "description": "Look up an order by id",        "parameters": {          "type": "object",          "properties": {            "orderId": {              "type": "string"            }          },          "required": [            "orderId"          ]        }      }    },    "code": "return { ok: true }"  }'
{
  "data": {
    "id": "V1StGXR8Z5jdHi6BmyT",
    "title": "lookup_order",
    "schema": {
      "type": "function",
      "function": {
        "name": "lookup_order",
        "description": "Look up an order by id",
        "parameters": {
          "type": "object",
          "properties": {
            "orderId": {
              "type": "string"
            }
          },
          "required": [
            "orderId"
          ]
        }
      }
    },
    "code": "return { ok: true }",
    "createdAt": "2026-06-01T09:14:00.000Z",
    "updatedAt": "2026-06-20T14:02:11.000Z"
  }
}
{
  "error": {
    "code": "BAD_REQUEST",
    "message": "Invalid request"
  }
}
{
  "error": {
    "code": "UNAUTHORIZED",
    "message": "API key required"
  }
}
{
  "error": {
    "code": "FORBIDDEN",
    "message": "Insufficient workspace permissions",
    "details": {
      "code": "INSUFFICIENT_WORKSPACE_ROLE"
    }
  }
}
{
  "error": {
    "code": "NOT_FOUND",
    "message": "Not found"
  }
}
{
  "error": {
    "code": "CONFLICT",
    "message": "API key name already exists"
  }
}
{
  "error": {
    "code": "PAYLOAD_TOO_LARGE",
    "message": "Request body is too large"
  }
}
{
  "error": {
    "code": "RATE_LIMITED",
    "message": "API rate limit exceeded",
    "details": {
      "retryAfter": "2026-01-01T00:00:30.000Z"
    }
  }
}
{
  "error": {
    "code": "INTERNAL_ERROR",
    "message": "Internal server error"
  }
}
{
  "error": {
    "code": "SERVICE_UNAVAILABLE",
    "message": "Service temporarily unavailable"
  }
}
PATCHUpdate SkillDELETEDelete Custom Tool