--- title: "Send Events" method: POST path: "/v1/sessions/{session_id}/events?beta=true" --- # Send Events `POST /v1/sessions/{session_id}/events?beta=true` ## Path parameters - `session_id` string, required ## Headers - `anthropic-version` string - `anthropic-beta` string ## Request body - BetaManagedAgentsSendSessionEventsParams — Request parameters for sending events to a `session`. - `events` BetaManagedAgentsEventParams[], required — Events to send to the `session`. - union — Union type for event parameters that can be sent to a session. - object — Parameters for sending a user message to the session. - `type` 'user.message', required - `content` BetaManagedAgentsUserContentBlock[], required — Array of content blocks for the user message. - union — Content block in a user message. Can be `text`, `image`, or `document`. - object — Regular text content. - … - object — Image content specified directly as base64 data or as a reference via a URL. - … - object — Document content, either specified directly as base64 data, as text, or as a reference via a URL. - … - object — Parameters for sending an interrupt to pause the agent. - `type` 'user.interrupt', required - `session_thread_id` string, nullable — If absent, interrupts every non-archived thread in a multiagent session (or the primary alone in a single-agent session). If present, interrupts only the named thread. - object — Parameters for confirming or denying a tool execution request. - `type` 'user.tool_confirmation', required - `tool_use_id` string, required — The id of the `agent.tool_use` or `agent.mcp_tool_use` event this result corresponds to, which can be found in the last `session.status_idle` [event's](https://platform.claude.com/docs/en/api/beta/sessions/events/list#beta_managed_agents_session_requires_action.event_ids) `stop_reason.event_ids` field. - `result` 'allow' | 'deny', required — UserToolConfirmationResult enum - `deny_message` string, nullable — Optional message providing context for a 'deny' decision. Only allowed when result is 'deny'. - object — Parameters for providing the result of a custom tool execution. - `type` 'user.custom_tool_result', required - `custom_tool_use_id` string, required — The id of the `agent.custom_tool_use` event this result corresponds to, which can be found in the last `session.status_idle` [event's](https://platform.claude.com/docs/en/api/beta/sessions/events/list#beta_managed_agents_session_requires_action.event_ids) `stop_reason.event_ids` field. - `content` BetaManagedAgentsToolResultContentBlock[] — The result content returned by the tool. - union — Content block in a tool result. Can be `text`, `image`, `document`, or `search_result`. - object — Regular text content. - … - object — Image content specified directly as base64 data or as a reference via a URL. - … - object — Document content, either specified directly as base64 data, as text, or as a reference via a URL. - … - object — A block containing a web search result. - … - `is_error` boolean, nullable — Whether the tool execution resulted in an error. - object — Parameters for defining an outcome the agent should work toward. The agent begins work on receipt. - `type` 'user.define_outcome', required - `description` string, required — What the agent should produce. This is the task specification. - `rubric` union, required — Rubric for grading the quality of an outcome. - BetaManagedAgentsFileRubricParams — Rubric referenced by a file uploaded via the Files API. - `type` 'file', required - `file_id` string, required — ID of the rubric file. - BetaManagedAgentsTextRubricParams — Rubric content provided inline as text. - `type` 'text', required - `content` string, required — Rubric content. Plain text or markdown — the grader treats it as freeform text. Maximum 262144 characters. - `max_iterations` integer, nullable — Eval→revision cycles before giving up. Default 3, max 20. - object — Parameters for providing the result of an agent-toolset tool execution. Only valid on `self_hosted` environments, where sandbox-routed tools are executed by the client rather than the server. - `type` 'user.tool_result', required - `tool_use_id` string, required — The id of the `agent.tool_use` event this result corresponds to, which can be found in the last `session.status_idle` [event's](https://platform.claude.com/docs/en/api/beta/sessions/events/list#beta_managed_agents_session_requires_action.event_ids) `stop_reason.event_ids` field. - `content` BetaManagedAgentsToolResultContentBlock[] — The result content returned by the tool. - union — Content block in a tool result. Can be `text`, `image`, `document`, or `search_result`. - object — Regular text content. - … - object — Image content specified directly as base64 data or as a reference via a URL. - … - object — Document content, either specified directly as base64 data, as text, or as a reference via a URL. - … - object — A block containing a web search result. - … - `is_error` boolean, nullable — Whether the tool execution resulted in an error. ## Response `200` Successful response (OK) - BetaManagedAgentsSendSessionEvents — Events that were successfully sent to the session. - `data` BetaManagedAgentsInputEvent[] — Sent events - union — Union type for events that can be sent to a session. - object — A user message event in the session conversation. - `type` 'user.message', required - `id` string, required — Unique identifier for this event. - `content` BetaManagedAgentsUserContentBlock[], required — Array of content blocks comprising the user message. - union — Content block in a user message. Can be `text`, `image`, or `document`. - object — Regular text content. - … - object — Image content specified directly as base64 data or as a reference via a URL. - … - object — Document content, either specified directly as base64 data, as text, or as a reference via a URL. - … - `processed_at` string, date-time — A timestamp in RFC 3339 format - object — An interrupt event that pauses agent execution and returns control to the user. - `type` 'user.interrupt', required - `id` string, required — Unique identifier for this event. - `processed_at` string, date-time — A timestamp in RFC 3339 format - `session_thread_id` string, nullable — If absent, interrupts every non-archived thread in a multiagent session (or the primary alone in a single-agent session). If present, interrupts only the named thread. - object — A tool confirmation event that approves or denies a pending tool execution. - `type` 'user.tool_confirmation', required - `id` string, required — Unique identifier for this event. - `tool_use_id` string, required — The id of the `agent.tool_use` or `agent.mcp_tool_use` event this result corresponds to, which can be found in the last `session.status_idle` [event's](https://platform.claude.com/docs/en/api/beta/sessions/events/list#beta_managed_agents_session_requires_action.event_ids) `stop_reason.event_ids` field. - `result` 'allow' | 'deny', required — UserToolConfirmationResult enum - `deny_message` string, nullable — Optional message providing context for a 'deny' decision. Only allowed when result is 'deny'. - `processed_at` string, date-time — A timestamp in RFC 3339 format - `session_thread_id` string, nullable — When set, the confirmation routes to this subagent's thread rather than the primary. Echo this from the `session_thread_id` on the `agent.tool_use` or `agent.mcp_tool_use` event that prompted the approval. - object — Event sent by the client providing the result of a custom tool execution. - `type` 'user.custom_tool_result', required - `id` string, required — Unique identifier for this event. - `custom_tool_use_id` string, required — The id of the `agent.custom_tool_use` event this result corresponds to, which can be found in the last `session.status_idle` [event's](https://platform.claude.com/docs/en/api/beta/sessions/events/list#beta_managed_agents_session_requires_action.event_ids) `stop_reason.event_ids` field. - `content` BetaManagedAgentsToolResultContentBlock[] — The result content returned by the tool. - union — Content block in a tool result. Can be `text`, `image`, `document`, or `search_result`. - object — Regular text content. - … - object — Image content specified directly as base64 data or as a reference via a URL. - … - object — Document content, either specified directly as base64 data, as text, or as a reference via a URL. - … - object — A block containing a web search result. - … - `is_error` boolean, nullable — Whether the tool execution resulted in an error. - `processed_at` string, date-time — A timestamp in RFC 3339 format - `session_thread_id` string, nullable — Routes this result to a subagent thread. Copy from the `agent.custom_tool_use` event's `session_thread_id`. - object — Echo of a `user.define_outcome` input event. Carries the server-generated `outcome_id` that subsequent `span.outcome_evaluation_*` events reference. - `type` 'user.define_outcome', required - `id` string, required — Unique identifier for this event. - `processed_at` string, date-time, required — A timestamp in RFC 3339 format - `outcome_id` string, required — Server-generated `outc_` ID for this outcome. Referenced by `span.outcome_evaluation_*` events and the session's `outcome_evaluations` list. - `description` string, required — What the agent should produce. Copied from the input event. - `max_iterations` integer, nullable, required — Evaluate-then-revise cycles before giving up. Default 3, max 20. - `rubric` union, required — Rubric for grading the quality of an outcome. - BetaManagedAgentsFileRubric — Rubric referenced by a file uploaded via the Files API. - `type` 'file', required - `file_id` string, required — ID of the rubric file. - BetaManagedAgentsTextRubric — Rubric content provided inline as text. - `type` 'text', required - `content` string, required — Rubric content. Plain text or markdown — the grader treats it as freeform text. - object — Event sent by the client providing the result of an agent-toolset tool execution. Only valid on `self_hosted` environments, where sandbox-routed tools are executed by the client rather than the server. - `type` 'user.tool_result', required - `id` string, required — Unique identifier for this event. - `tool_use_id` string, required — The id of the `agent.tool_use` event this result corresponds to, which can be found in the last `session.status_idle` [event's](https://platform.claude.com/docs/en/api/beta/sessions/events/list#beta_managed_agents_session_requires_action.event_ids) `stop_reason.event_ids` field. - `content` BetaManagedAgentsToolResultContentBlock[] — The result content returned by the tool. - union — Content block in a tool result. Can be `text`, `image`, `document`, or `search_result`. - object — Regular text content. - … - object — Image content specified directly as base64 data or as a reference via a URL. - … - object — Document content, either specified directly as base64 data, as text, or as a reference via a URL. - … - object — A block containing a web search result. - … - `is_error` boolean, nullable — Whether the tool execution resulted in an error. - `processed_at` string, date-time — A timestamp in RFC 3339 format - `session_thread_id` string, nullable — Routes this result to a subagent thread. Copy from the `agent.tool_use` event's `session_thread_id`. ## Other responses - `400` — Invalid argument - The client specified an invalid argument - `401` — Unauthenticated - The request does not have valid authentication credentials - `403` — Permission denied - The caller does not have permission to execute the specified operation - `404` — Not found - Some requested entity was not found - `408` — Deadline exceeded - The deadline expired before the operation could complete - `409` — Aborted - The operation was aborted due to concurrency issue - `412` — Failed precondition - Operation was rejected because the system is not in required state - `413` — Out of range - Operation was attempted past the valid range - `429` — Resource exhausted - Some resource has been exhausted (rate limiting) - `431` — Request header fields too large - Request metadata was too large - `499` — Cancelled - The operation was cancelled by the client - `500` — Internal - Internal server error - `501` — Unimplemented - The operation is not implemented or supported - `503` — Unavailable - The service is currently unavailable - `504` — Deadline exceeded - Upstream service did not respond in time ## Changes - **2026-05-19** `40e330aba8bc` — 1 breaking, 3 info - added `#/components/schemas/BetaManagedAgentsUserToolResultEvent` to the `data/items/` response property `oneOf` list for the response status `200` - added `user.tool_result` discriminator mapping keys to the `events/items/` request property - added `#/components/schemas/BetaManagedAgentsUserToolResultEventParams` to the `events/items/` request property `oneOf` list - added `user.tool_result` discriminator mapping keys to the `data/items/` response property for the response status `200` - **2026-05-13** `88ef81f4f457` — 1 breaking, 1 warning - removed the required property `data/items/oneOf[#/components/schemas/BetaManagedAgentsUserCustomToolResultEvent]/content/items/oneOf[#/components/schemas/BetaManagedAgentsSearchResultBlock]/tool_use_id` from the response with the `200` status - removed the request property `events/items/oneOf[#/components/schemas/BetaManagedAgentsUserCustomToolResultEventParams]/content/items/oneOf[#/components/schemas/BetaManagedAgentsSearchResultBlock]/tool_use_id` - …earlier changes not shown [Full history](https://skmtc.dev/anthropics/apis/anthropic-api/changes/v1/sessions/:session_id/events?beta=true/post.md) --- [API](https://skmtc.dev/anthropics/apis/anthropic-api.md) · [All operations](https://skmtc.dev/anthropics/apis/anthropic-api/llms.txt) · [OpenAPI document](https://skmtc.dev/anthropics/apis/anthropic-api/revisions/478045ff0f4f?raw)