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

Annotations only cover the safety profile (readOnly, idempotent, openWorld, non-destructive), while the description adds pricing ($0.001 per call, 10 free/day, payment-required result listing x402 options), error behavior (isError, not charged on failure), data provenance (OpenStreetMap via Photon), and returned OSM links. That is substantial context beyond the structured fields.

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 core purpose is front-loaded with arrow notation, then clearly labeled 'When to use', 'Price', and 'Errors' sections. Every clause carries information with 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?

With an output schema present, return values need not be explained, yet the description still notes city/state/country/postcode fields and OSM links. Pricing, error handling, data source, and limits are all covered for this moderately simple two-parameter tool.

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 both parameters are already documented, including the limit range and the 'address/place, or lat,lon for reverse' query format. The description largely restates these (limit → 'up to 10 candidates', reverse via lat,lon) rather than adding new syntactic or format detail, so baseline 3 is appropriate.

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 states a specific verb (geocode/reverse geocode) and resource (place name or address → coordinates, or lat,lon → nearest address), and explicitly covers both directions of the operation. An agent can immediately tell what the tool produces without opening the schema.

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?

Includes an explicit 'When to use' clause ('To turn names into coordinates') and points out that weather and sun_moon accept place names directly, routing the agent away from unnecessary calls. It does not state an explicit when-not condition, keeping it just short of the top mark.

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