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

Annotations already declare readOnly/idempotent/non-destructive, but the description adds real behavioral detail beyond them: exact/lexical lookup with no model or embeddings, token-prefix support, bounded typo tolerance, and the coverage caveat about unsearched families. The 'Free' note is a useful cost signal. Slight overlap with the output schema on return structure keeps it from a 5.

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?

Front-loaded with purpose and accepted inputs, then alternatives, then caveats; no filler sentences. It is dense and runs long, but nearly every clause carries routing or behavioral information.

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?

With an output schema present, return values need not be described, and the description covers routing, lookup semantics, coverage limits, and cost. The only real gap is the limit parameter's behavior and whether it applies per-family or overall.

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 0%, so the description carries the burden. It does clarify what q accepts (title/address text, postcode, UUID, prefixes, typo tolerance), which is genuinely useful. However, 'limit' is never mentioned, and its interaction with the 'separate families' result structure is left unexplained.

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 (find public records) plus the accepted key types (title/address text, postcode, public UUID). It also names the sibling tools it is not (address_autocomplete, address_by_uprn, search_entities), so an agent can route without opening any schema.

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?

Explicit when-to-use-this and when-to-use-an-alternative: full address matching goes to address_autocomplete, a UPRN goes to address_by_uprn, attribute criteria go to search_entities. It also states the negative case (an unlisted family was not searched, no match does not prove nonexistence).

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