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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint=false, so safety is covered. The description adds genuinely new behavioural context beyond them: the result is a self-declared claim, not verified proof, which affects how much an agent should trust the response. It does not mention match confidence or fallback behaviour when nothing matches.

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?

Three short sentences, front-loaded with the core purpose, then the trust caveat, then the sibling routing and precondition. The catalog enumeration is long but earns its place by defining the match universe.

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 lookup with full schema coverage and annotations, the description covers purpose, trust level, alternative and minimum input. Without an output schema, the return shape (e.g. matched entry versus no-match) is still left implicit, which is the only notable gap.

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 coverage is 100%, so the baseline is 3, but the description adds meaning: it clarifies that client_name is the MCP clientInfo.name sent in initialize and that at least one of the two optional parameters must be supplied, filling the gap left by required=0.

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 (identify who a User-Agent / clientInfo.name claims to be) and scopes the matching source to criba's catalog with named categories of entries. It is clearly separable from classify_visitor, which the description itself names as the behavioural counterpart.

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: use this tool for declared identity, use classify_visitor for behaviour. It also states the invocation constraint 'Pass at least one of the two', which is a concrete precondition rather than an inference.

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