Call schema reference

Reference for the Call object structure and properties

This reference describes the Call object schema in W&B Weave, including its properties, how to write custom data to the summary dictionary during execution, and how to read summary data after a Call completes. Use this page when you need to inspect, filter, or extend the data Weave records for each Call. For information about querying calls, see Query and export calls.

Call properties

The following table outlines the key properties of a Call in Weave. For the complete implementation, see the following:

• class: CallSchema in the Python SDK
• Interface: CallSchema in the TypeScript SDK

Property	Type	Description
id	string (uuid)	Unique identifier for the Call
project_id	string (optional)	Associated project identifier
op_name	string	Name of the operation (can be a reference)
display_name	string (optional)	User-friendly name for the Call
trace_id	string (uuid)	Identifier for the trace this Call belongs to
parent_id	string (uuid)	Identifier of the parent Call
started_at	datetime	Timestamp when the Call started
attributes	Dict[str, Any]	User-defined metadata about the Call (read-only during execution)
inputs	Dict[str, Any]	Input parameters for the Call
ended_at	datetime (optional)	Timestamp when the Call ended
exception	string (optional)	Error message if the Call failed
output	Any (optional)	Result of the Call
summary	Optional[SummaryMap]	Post-execution summary information. You can modify this during execution to record custom metrics.
wb_user_id	Optional[str]	Associated W&B user ID
wb_run_id	Optional[str]	Associated W&B run ID
deleted_at	datetime (optional)	Timestamp of Call deletion, if applicable

Property details

CallSchema properties help you track and manage Calls:

• The id, trace_id, and parent_id properties help organize and relate Calls within the system.
• Timing information (started_at, ended_at) supports performance analysis.
• The attributes and inputs properties provide context for the Call. Attributes are frozen once the Call starts, so set them before invocation using the weave.attributes() context manager. output and summary capture the results.
• Use wb_user_id and wb_run_id to link the Call to a W&B user and run.

Together, these properties support detailed tracking and analysis of Calls throughout your project.

Use Call summary

Use the summary property to attach custom, post-execution data to a Call so you can analyze it later alongside Weave’s built-in metrics. It’s a dictionary you can write to during a Call’s execution. When the Call finishes, Weave deep-merges your values with its own computed data and stores the result.

The dictionary has two zones:

• Your custom keys: anything you write to call.summary directly, such as call.summary["accuracy"] = 0.95. These sit at the top level of the summary dict.
• summary["weave"]: a reserved namespace Weave populates automatically at Call completion. Don’t write to this key directly.

Weave also captures raw LLM token counts from the model response at summary["usage"] (keyed by model name). This is source data passed through from the provider, not a Weave computation. The costs field inside summary["weave"] is what Weave derives from that usage data using token pricing.

Weave’s computed fields inside summary["weave"]:

Field	Description
status	Execution status: SUCCESS, ERROR, RUNNING, or DESCENDANT_ERROR (the Call succeeded but a child Call errored).
latency_ms	Duration in milliseconds between started_at and ended_at. null if status is RUNNING.
costs	Cost breakdown per model, derived from summary["usage"] and token pricing data. See Track costs.
trace_name	Human-readable Op name, parsed from the internal Op reference URI. Used for display and filtering.

Write during a Call

You can add custom data values during your Call using the summary dictionary.

Python

In Python, assign values to call.summary at any point during execution using weave.get_current_call().

import weave

@weave.op()
def my_op(x):
    result = do_work(x)
    call = weave.get_current_call()
    # Add custom data values to the summary.
    call.summary["accuracy"] = 0.95
    call.summary["num_retries"] = 2
    return result

TypeScript

In TypeScript, provide a summarize function as an option to op(). It receives the final result and returns summary data at Call completion.

const myOp = weave.op(
  async (x: any) => {
    const result = await doWork(x);
    return result;
  },
  {
    name: 'my_op',
    summarize: (result) => ({
      accuracy: result.accuracy,
      numRetries: result.numRetries,
    }),
  }
);

Read summary data

Use getCall to fetch a single Call by ID, or getCalls to fetch multiple Calls. In both cases, summary is the same merged dictionary.

Python

import weave
client = weave.init("my-team/my-project")

# Fetch a single Call by ID.
call = client.get_call("[CALL-ID]")
weave_summary = (call.summary or {}).get("weave", {})

print(weave_summary.get("status"))       # TraceStatus enum: SUCCESS, ERROR, RUNNING, or DESCENDANT_ERROR.
print(weave_summary.get("latency_ms"))   # Null if the Call is still running.
print(weave_summary.get("costs"))        # Cost breakdown per model.
print(call.summary.get("usage"))         # Raw token counts from the LLM provider.
print(call.summary.get("accuracy"))      # Your custom field.

# Iterate over multiple Calls with server-side filtering.
for call in client.get_calls(filter={"op_names": ["weave:///my-team/my-project/op/my_op:*"]}):
    s = call.summary or {}
    weave_s = s.get("weave", {})
    print(call.id, weave_s.get("status"), weave_s.get("latency_ms"), s.get("accuracy"))

TypeScript

import * as weave from 'weave';
const client = await weave.init('my-team/my-project');

// Fetch a single Call by ID.
const call = await client.getCall('[CALL-ID]');
const weaveSummary = call.summary?.weave;

console.log(weaveSummary?.status);       // "success", "error", "running", or "descendant_error".
console.log(weaveSummary?.latency_ms);   // Undefined if the Call is still running.
console.log(weaveSummary?.costs);        // Cost breakdown per model.
console.log(call.summary?.usage);        // Raw token counts from the LLM provider.
console.log(call.summary?.accuracy);     // Your custom field.

// Fetch multiple Calls with server-side filtering.
const calls = await client.getCalls({ filter: { op_names: ['weave:///my-team/my-project/op/my_op:*'] } });
for (const call of calls) {
  const weaveS = call.summary?.weave;
  console.log(call.id, weaveS?.status, weaveS?.latency_ms, call.summary?.accuracy);
}