Reference: Limits and Errors

Limits

Limit	Value
Triggers per action	16
Trigger expression size	16 KiB
Expressions in a trigger `view`	64
`session.schedule` entries	8
`every` in a `session.schedule` entry	Whole minutes, at least 1m
`turns.window`	24h
A view as the agent reads it	4 KiB
Configuration size	352 KiB
Event and handler output size	1 MiB
Samples per `validateAction` call	100
Page size (`first`)	1 to 100
`maxInvocations`	24
`timeout`	24h
`retryDelay` and `maxRetryDelay`	12h
`responseTimeout`	10m
`completionTimeout`	24h
Tools an MCP server references	128
Tool levels below a first call	8
Calls beneath one call	1,024
Agents in one call chain	3
Output uses per invocation	256
Transcript events per invocation	4,096
Starlark source	64 KiB
Starlark steps per invocation	1,000,000
`graphql`, `cel`, and `tools` calls per Starlark invocation	64 each
A `cel` expression from Starlark	16 KiB; aggregate CEL cost 100,000

Errors

Errors follow the API error format. Reads of an identifier that was never created return null rather than an error. A request refused because it conflicts with what is recorded, such as rerunning a replay or an unfinished execution, replaying a replay, or answering an approval request twice, has code BAD_REQUEST and is not retriable: the same request is refused the same way.

Situation	Result
`updateAction`, `deleteAction`, `cancelExecution`, `rerunExecution`, or `replayExecution` on an identifier that was never created	Error with code `NOT_FOUND`.
Invalid trigger, configuration, policy, or execution setting on create, update, or validation	Error whose message names the rejected setting, for example `retry delay cannot exceed the maximum retry delay`.
More than 16 triggers, or no trigger, `tool` block, kind `skill`, or kind `mcp`, on create, update, or validation	Error `an action accepts at most 16 triggers`, or `an action requires a trigger, a tool block, kind skill, or kind mcp`.
A name already used by another action, or a `tools` or `skills` entry that cannot be resolved	Error; the write is rejected.
An invalid `schedule`, `cron`, `timezone`, `every`, or `session.ends`, or a schedule trigger without a name or resuming by `input`	Error whose message names the rejected setting, for example `session.schedule[0].every: every 1m30s: must be whole minutes`.
`session.ends`, `session.schedule`, or a schedule trigger in a deployment without a scheduler	Error `this deployment has no scheduler: session.ends, session.schedule, and schedule triggers are unavailable`.
A session turn that reports `COMPLETED` before the session's end, or `OPEN` in its final turn	The turn fails with `action_output_invalid`. An agent is offered only the allowed status.
A skill whose name is also a tool name the action's model sees	Error `tool and skill names must be distinct within one action`.
An agent's call to a tool or skill version it does not pin	Permission error carrying the code `tool_not_declared`.
A call to a tool whose session is closed	Error with code `INVALID_STATE_TRANSITION` carrying `session_closed`; nothing runs or is recorded.
A skill load whose input is not an empty object	Error `a skill load takes an empty input object`.
`invokeAction` on a disabled, deleted, or unpublished tool, a native tool that acts for its caller, or without `INVOKE` permission	Error that is not retriable, with code `NOT_SUPPORTED` or `ACCESS_DENIED`, whose `actionError` extension carries the reason's `code`, such as `action_not_callable` or `action_access_denied`, with a `message` and `hint`; nothing runs or is recorded.
`startAction` on a disabled, deleted, or unpublished action, one without a `tool` block, a tool with a session, from inside an execution, without `INVOKE` permission, or with input that fails the schema	Error that is not retriable, with code `NOT_SUPPORTED`, `ACCESS_DENIED`, or `BAD_REQUEST`, whose `actionError` extension carries the reason's `code`, such as `action_not_callable`, `start_not_supported`, `action_access_denied`, or `action_input_invalid`, with a `message` and `hint`; nothing is queued or recorded. In gRPC, the status carries them as an `ErrorInfo` detail: `reason` is the code, and `metadata.hint` the hint. From inside an MCP request, run the action with `invoke` instead, on a server that lists it.
`startAction` of a native tool that acts for its caller, such as `program`, `invoke`, `read_turn_input`, or a harness tool, or `rerunExecution` of a call to one	Error that is not retriable, with code `NOT_SUPPORTED` and `actionError` code `start_not_supported`: such a tool runs only as its caller's call. Nothing is queued or recorded.
`startAction` with an `executionId` already used with a different principal, action, version, or input	Error with code `ALREADY_EXISTS`, not retriable; an execution identifier names one start.
An invocation of a started execution after its starter was revoked, may no longer invoke the action, or its token expired	The execution fails with `action_access_denied`; nothing of the invocation runs.
`invokeAction` with input that fails the tool's schema, or a call that fails	A `FAILED` execution whose `invocation.error` carries the code and a hint; the caller can still commit.
A write conflict, passed deadline, or interrupted transaction during a call	Retryable error; roll back and retry in a new transaction.
Kind `workflow.starlark`, a `tool` block on a kind other than `tool`, `agent`, or a native tool's, or kind `tool` without one	Error; kind `tool` with config `{runtime, src}` replaces `workflow.starlark`.
An agent whose schemas do not combine into its turn outcome, whose limits could derive more than 256 uses, or whose references read `tool.input` while it has triggers	Error whose message names the rule.
An action named after a native tool, such as `graphql`, `cel`, or `read_turn_input`	Error; the names are reserved for native tools.
Update or delete of a deleted action	Error; the action is immutable after `pending: DELETED`.
`rerunExecution` of an intake record whose action is disabled or deleted, at a version without a `session`, or at a version whose triggers are no longer published	Error whose message names the reason; nothing is created.
`rerunExecution` on a non-terminal source, or `executionId` reuse with different values	Error; the source must be terminal and an execution identifier names one rerun.
`replayExecution` on an unfinished execution, a call another execution made, a replay, an intake record, an action that is not kind `agent` or `mcp`, or with a version whose session does not match the source's	Error whose message names the reason; nothing is created.
`rerunExecution` of an MCP server's request	Error; a request runs only when its endpoint serves it. Replay it instead.
`rerunExecution` or `replayExecution` of a draft's preview, an execution with a `draft`	Error; no version holds the draft it ran. Preview the draft again.
`rerunExecution` or `replayExecution` without `INVOKE` on the action, or `rerunExecution` from inside an execution	Error; nothing is queued or recorded. From inside an MCP request, run the action with `invoke` instead, on a server that lists it.
`rerunExecution` of a call to a tool with a session, or of a call or start whose action is no longer callable	Error whose message names the reason; nothing is queued. Call the tool again instead.
`replayExecution` with `executionId` reuse with different values	Error; an execution identifier names one replay.
`cancelExecution` on an execution processing a session turn	Error; close the session instead.
Explicit `null` on an update field outside `execution`	Error; omit the field to preserve it.
An execution listing with `intake: true` and, in the gRPC `ListActionExecutions`, a `session_id` or `parent_execution_id`	Error; intake records run no turn and make no call.
Cursor from a different filter, or `first` outside 1 to 100	Error.

Because operations inside one actions block share a transaction, an error in any of them aborts all of them.