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

Discloses metered token cost (1 token per returned row) and that rows carry a numeric mode_id. Indicates it is a read-only query. Without annotations, the description provides useful behavioral context beyond the schema, though it could mention result structure or limits more explicitly.

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 sentences, front-loaded with the main purpose, no redundant words. Each sentence adds essential information: purpose, area specification, token cost, and output hint.

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?

Given no output schema and no annotations, the description covers the main purpose, area methods, token cost, and a hint about output format. The 7 parameters are fully described in the schema. Missing details like exact output columns or pagination, but sufficient for an agent to invoke correctly.

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% with each parameter described. The description adds meaning by clarifying the mutual exclusivity of place_geoid vs lat/lon/radius and the source of place_geoid (find_place). This contextualizes parameter usage beyond the schema descriptions.

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?

Description clearly states the tool returns per-block travel times for an area, with two area specification methods (place_geoid or lat/lon/radius). This verb+resource is specific and distinguishes from sibling tools like isochrone or nearby_pois.

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?

Provides explicit guidance on how to specify the area: using place_geoid from find_place for a whole city, or center lat/lon+radius. Mentions token cost as a usage consideration. Does not explicitly state when not to use or compare to alternatives, but the context is clear enough.

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