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

Annotations already declare readOnlyHint and openWorldHint, so safety and external-network behavior are covered. The description adds real value by identifying the backend contract (Nominatim JSONv2) and noting that zoom and detail flags control returned address fields. It omits any mention of upstream rate limits or usage policy, which matters for a public Nominatim endpoint, so it stops short of a 5.

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, zero filler, with the core operation front-loaded and the sibling routing in the second sentence. Every clause earns its place.

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?

An output schema exists, so return values need no explanation, and the annotations plus schema cover safety and parameters. The description gives the agent enough to call correctly; the only omitted item is the upstream service's usage/rate constraints.

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 description coverage is 100%, so the seven parameters are already fully documented, including ranges, defaults, and the zoom scale. The description only gestures at 'zoom and detail flags' generically, adding no syntax or semantics beyond the schema. Baseline 3 is correct.

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 (fetch) and resource (nearest Nominatim JSONv2 place record) bound to lat/lon, and names the two sibling tools it must not be confused with. An agent can differentiate it from geocoding_lookup and geocoding_search without opening any 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?

Explicitly routes the agent: geocoding_lookup for a named place, geocoding_search for forward text search, leaving this tool for coordinate-to-place resolution. The selection condition is unambiguous.

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