Custom tools and MCP

Custom Tools connect an assistant to individual HTTP endpoints; MCP connects it to a tool server. The supported authentication schemes are Bearer, API Key, OAuth2, and HMAC.

Review available tools with GET /catalog/tools and the tools assigned to an assistant with GET /catalog/assistants/{assistantId}/tools. Apply runtime tool bindings with PATCH /assistants/{assistantId}/runtime/tools:

{
  "tools": [{
    "toolName": "crm_lookup",
    "subscriptionName": null
  }]
}

tools adds named tools to the current state; deleteTools removes them. For a classic custom_tool, subscriptionName must be null. For plugin_tool and custom_mcp_tool, reuse the instanceName returned by the catalog.

Use least-privilege credentials and keep tool responses bounded so they remain useful to the model.