The usage summary of a period by model or by agent

Groups the sessions GET /v1/usage/summary adds up by the model their metered calls named (by=model) or by their agent (by=agent), largest cost first, with the input, output, cache read and cache write tokens of those calls. scope, since, until and who may read which scope are exactly the summary's; the period spans at most 366 days.

token_count is the four token columns' sum; the 1-hour cache writes are inside cache_creation_input_tokens. totals is the summary of the same period: its session_count, token_count and cost_usd equal it.

• by=agent: each session counts once under its agent (key is the agent id, label its name), so the rows add up to totals in every column. Sessions without an agent are the row whose key and label are null.
• by=model: a session counts under every model it called, so the rows' session_count may add up to more than the totals'. A session's cost its metered calls do not explain, such as an engine's turn totals from before proxy metering, is the row whose key and label are null, with no tokens.

It changes nothing.

Scope: sessions:read (API key or cookie session).