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

Annotations already declare readOnlyHint=true and destructiveHint=false. The description adds value by specifying that the list contains 'searchable pickup cities' and that it's for finding 'valid city names before searching,' which gives context beyond the annotations. No contradiction.

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: the first states the core function, the second gives a direct usage hint. No redundant words or vague filler. It is appropriately front-loaded and easy to parse.

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 simple tool with one optional parameter and no output schema, the description is complete. It explains what the tool returns (searchable pickup cities), how to filter (by country), and when to use it (before searching). No additional information is necessary.

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%: the 'country' parameter is fully documented with examples ('e.g. AU, NZ, US') and behavior ('Omit to return all supported countries'). The description's mention of 'by country' aligns with the schema but doesn't add extra semantic detail beyond what's already in the parameter description.

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 clearly states the tool's purpose: 'List all searchable pickup cities by country.' This uses a specific verb (list) and resource (searchable pickup cities), and explicitly distinguishes it from the sibling tool 'search_campervans' by focusing on locations rather than campervans.

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 provides clear usage context: 'Call this to find valid city names before searching.' This tells the agent when to use the tool, though it doesn't explicitly mention alternatives or exclusions. The implied workflow (get cities, then search) is helpful.

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