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

Annotations already declare readOnlyHint=true, but the description adds meaningful context: 'Nothing is booked' pre-empts confusion over the POST endpoint, and 'Stuart: POST /v2/jobs/eta' discloses the underlying call. It doesn't cover error/rate-limit behavior, but the key mutation-vs-read ambiguity is resolved.

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?

Two short sentences and the endpoint reference, with the return value front-loaded. No 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 nested, 3-parameter tool with no output schema, the description states the return unit (seconds) and clarifies the no-booking behavior. Adequate, though it could note the dropoff ETA sibling distinction more explicitly.

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?

Schema coverage is 100%, so the baseline is 3, and the description earns extra credit by telling the agent the body mirrors create ('same job body as create'), which meaningfully guides parameter construction beyond the schema itself.

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?

States a specific verb and resource ('Estimated seconds until a courier could arrive at the pickup address') and implicitly distinguishes itself from the sibling stuart_estimate_dropoff_eta by anchoring to the pickup. The 'same job body as create' clause ties it to a known sibling's shape.

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?

'Nothing is booked' clearly signals this is a non-committal quote, and 'same job body as create' tells the agent what to supply. It stops short of explicitly contrasting with stuart_estimate_price or stuart_estimate_dropoff_eta, but the conditions for use are clear.

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