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

Annotations already communicate read-only and idempotent behavior, so the description doesn't need to repeat those. The description adds behavioral detail by specifying the output types (address, street, place) and the 'nearest' qualifying behavior, which goes beyond the tool name and annotations.

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 description is two sentences long, with the primary purpose stated first and usage guidance in the second sentence. Every word earns its place; there is no redundancy or 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?

Given the presence of a complete input schema, output schema, and annotations (readOnlyHint, idempotentHint), the description covers the essential context. It does not need to explain return values or parameter details since the schema and annotations already do so, and the description is adequate for tool selection.

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%, with all four parameters (lat, lon, size, layers) already clearly described in the schema. The tool description adds no additional parameter meaning beyond the schema, so the baseline score of 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 uses a specific verb ('Convert coordinates into') and identifies the resource ('nearest address, street, or place'), which clearly defines the tool's function. It distinguishes itself from the sibling 'geocode' by emphasizing the reverse direction (starting from coordinates), making the purpose unambiguous.

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?

The description explicitly says 'Use when starting from GPS coordinates or a map position,' providing clear context for when the tool is appropriate. It does not mention alternatives or exclusions, but the guidance is sufficient for this simple reverse-geocoding tool.

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