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

Annotations already declare readOnlyHint=true and openWorldHint=false. The description adds real behavioral context beyond that: results are ordered closest-first, and critically, it discloses a prerequisite – both sites must have been embedded, since results are read from a stored vector.

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, purpose front-loaded, no padding. The clause 'Read from one vector a site kept in the catalog' is a slightly awkward construction but still earns its place by conveying the embedding prerequisite.

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 two-parameter read-only tool with full schema coverage and no output schema, the description covers purpose, ordering, and the embedding precondition. Only the sibling differentiation and limit behavior are missing, which are minor for this complexity.

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% and both parameters (site as a domain, limit as count) are documented in the schema. The description reinforces 'one site' but adds no format, default, or range detail for limit, so baseline 3 applies.

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 operation (returning sites closest in meaning to one site, ordered closest first) and even characterizes the result as 'likeliest rivals'. It does not, however, distinguish itself from close siblings like mttr_similar or mttr_competitors, leaving ambiguity about which similarity tool to pick.

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?

There is a hint of use ('its likeliest rivals'), but no explicit when-to-use, when-not-to-use, or named alternative. With siblings mttr_similar and mttr_competitors present, the agent receives no guidance on choosing among them.

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