Declaration of what a given model/provider supports, so callers and future capabilities can negotiate gracefully per model — e.g. whether the provider can do native JSON-schema output, forced tool calls, or extended thinking.

Every model returns one via the optional ExAgent.Model.profile/1 callback; providers that don't implement it get conservative defaults: extra capabilities are not negotiated until explicitly declared. Basic text needs no capability flag.

The core enforces supports_tools for function tools and tool-based structured output. It rejects unsupported requirements instead of silently downgrading. Native JSON and thinking flags remain advisory for features not selected by the current tool-output mode; supports_json_schema_output: false therefore does not disable Ecto output through a tool. Streaming requires the optional model callback and is not required for a synchronous custom model.

accounting_quality declares a known metric contract for preflight: :normalized cannot satisfy strict metric thresholds. The default :unknown permits the operation and checks its actual host report before subsequent effects; it is not a guarantee of provider presence or available pricing.