List available engines and models

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare read-only, idempotent, non-destructive behavior. The description adds valuable behavioral context: the list is a live snapshot of what the platform can serve right now, prices are in micro-USD, engines are either composed or realtime, and provider degradation causes engines to disappear before failures occur.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is compact and front-loaded: it starts with the core purpose and pricing, then explains engine composition, then gives the usage rule. Every sentence contributes distinct information without filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a zero-parameter, read-only list tool, the description is remarkably complete. It explains what is returned, the pricing unit, the composed-vs-realtime distinction, the dynamic availability behavior, the recommended usage in the create_agent flow, and the only prerequisite. No output schema exists, but the description provides enough context to call the tool confidently.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The tool has zero parameters and the schema provides 100% coverage by defining an empty object. The description still adds useful context by clarifying that no scope is needed beyond a valid key, which is helpful authentication/scoping information.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly identifies a list operation over the engines/models resource, states that it returns what the platform can currently serve, and includes per-unit prices in micro-USD. It also distinguishes itself from the create_agent workflow by saying to call it before create_agent rather than guessing model ids.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description gives explicit when-to-use guidance: call this before create_agent instead of guessing model ids. It also explains why this matters—degraded providers disappear from the list before calls start failing—and states the only prerequisite is a valid key.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.