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

Annotations only declare non-read-only, non-idempotent, open-world; the description goes well beyond by explaining the scoring model (traffic duration/delay, heat/cold against the lane ceiling, rain/snow/gusts), that lower is better, that scores are only comparable within one computation, that the best route is marked chosen, and that it degrades to a time-only ranking when routing or weather data is missing.

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?

Three sentences, front-loaded with the core action and followed by scoring semantics and the degradation caveat. Dense but nearly every clause carries information; the 'relay that' aside is the only slightly stray instruction.

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 complex, output-less tool the description covers what is computed, how it is scored, comparability limits, and failure/degradation behavior. It does not describe the shape of the returned route list or how many routes are ranked, a modest gap given no output schema exists.

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 50%: depart_at is documented as ISO 8601 with a default, shipment_id is bare. The description re-states 'at a departure time' and 'for a shipment' but adds no format, default, or identity semantics beyond the schema, so it only partially compensates for the uncovered parameter.

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 pair and resource: 'Compute and rank routes for a shipment at a departure time.' Route ranking is not offered by any sibling (create_shipment, shipment_status, list_shipments, trace_unit), so the agent can place it immediately.

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?

Usage is implied rather than stated: the agent learns the tool scores a shipment's route, but there is no explicit 'use this when...' or 'do not use when...'. The instruction to relay degraded (time-only / straight-line) results is useful operational guidance but is about output handling, not tool selection.

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