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> For a complete documentation index, see https://docs.nvidia.com/nemo/relay/llms.txt.
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# Function nemo_relay_tool_call

> Begin a manual tool call lifecycle span.

Generated from `cargo doc --no-deps -p nemo-relay -p nemo-relay-adaptive -p nemo-relay-pii-redaction -p nemo-relay-ffi -p nemo-relay-types -p nemo-relay-plugin -p nemo-relay-worker-proto -p nemo-relay-worker`.

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Begin a manual tool call lifecycle span.

This emits a tool Start event after applying sanitize-request guardrails to the observability payload. Request and execution intercepts only run through `nemo_relay_tool_call_execute`.

## Parameters

* `name`: Null-terminated tool name.
* `args_json`: Tool arguments as a null-terminated JSON C string. These arguments become the start-event data after sanitize-request guardrails.
* `parent`: Optional parent scope handle, or null to use the current top of stack.
* `attributes`: Bitfield of tool attributes.
* `data_json`: Optional null-terminated JSON string stored on the tool handle, or null.
* `metadata_json`: Optional null-terminated JSON metadata string recorded on the start event, or null.
* `tool_call_id`: Optional null-terminated external correlation ID recorded in the tool event category profile, or null.
* `timestamp_unix_micros`: Optional Unix microseconds timestamp for the handle start time and start event, or null to use the current UTC time.
* `out`: On success, receives a heap-allocated `FfiToolHandle` that must be freed with `nemo_relay_tool_handle_free`.

## Errors

Returns `InvalidJson` for invalid JSON inputs and `InvalidArg` when `timestamp_unix_micros` is outside the supported timestamp range.

## Safety

`name` and `args_json` must be valid C strings. `out` must be non-null. Optional pointer arguments may be null; when non-null, they must be valid for reads for the duration of the call.