Agent Completions 403: service_account_agent_completions_unsupported

A service-account key cannot create Agent Completions. POST /v1/agent/completions fails with 403 insufficient_scope and details.reason set to service_account_agent_completions_unsupported, and no scope can be added to change that.

This comes from Sume's Agent Completions page. A different cause produces the same 403 insufficient_scope, an older key without the new scopes, so the details.reason field is how you tell them apart.

Which two things cause this 403?

Both return the same status and code.

Which scopes does a working key need?

agent_completions:write creates a completion and cancels a run. agent_completions:read reads and lists runs. A key that can create but not read cannot poll its own run, so give a backend both.

What do I do about it?

Create a key at the dashboard's API Keys page and use it for this call. The docs link Authentication for how keys and rotation work.

After the 403 clears, the next error you are likely to see is 400 invalid_request, because generation_spend_cap_usd is required and has no default. The page explains why: the interactive spend-approval prompt is not available to a backend caller, so the cap replaces it.

Does a Format run behave the same way?

The Agent Completions page covers only its own endpoint. For the Format and Scheduled run endpoints, read their own pages: the same code can have a different cause there.