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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered. The description adds genuinely non-obvious behavioral context: coverage is the complete brand directory including brands with no active listings, which sets expectations about result breadth beyond what the annotations state.

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?

One dense sentence that front-loads what the tool is, then the scope caveat, then the motivating use case. No filler sentences.

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 parameterless directory lookup with an output schema and readOnly annotations, the description covers identity, scope, and the integration purpose. Everything an agent needs to select and call it correctly is present.

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?

The tool takes zero parameters, so the baseline is 4; there is nothing for the description to clarify about inputs. It does describe the output tuple (id, name, url), which is slight extra value though the output schema already carries it.

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 and resource ('full brand directory') and enumerates the returned fields (id, name, url). It explicitly contrasts itself with the narrower alternative ('not just brands with active listings'), so an agent can distinguish it from vestiaire_search and other vestiaire_* siblings without opening schemas.

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?

Gives a concrete use case — resolving vestiaire_search's brand_id filter to human-readable names — which tells the agent when this tool is the right follow-up call. It doesn't spell out when NOT to use it or name the suggestions sibling, so it falls just short of full when/when-not guidance.

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