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

With no annotations, the description carries the full behavioral burden. The credit-cost note is a genuinely useful disclosure, but nothing is said about matching behaviour (exact vs fuzzy name search), result caps or pagination, or error behaviour when the register has no match. It also doesn't clarify whether the search returns full authorisation detail or just identifiers.

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 compact sentences, front-loaded with what is searched and what it returns conceptually, with the cost tacked on in parentheses. Nothing is wasted, though the parenthetical cost would read better as a structured field than as trailing prose.

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?

This is a simple two-parameter read-only search with a fully described schema and no output schema, so the description is broadly sufficient to call it. It remains thin on result shape and matching semantics, which matter for an agent deciding whether a search hit is authoritative.

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 schema already documents both parameters and the baseline is 3. The description's "firms or individuals" loosely mirrors the type enum, but it adds no syntax, format, or matching guidance for the query string beyond what the schema states.

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 names a specific verb ("Search") and resource ("FCA Financial Services Register") and scopes it to "authorised firms or individuals," which implies the type parameter. It does not explicitly differentiate itself from look-alike siblings such as company_search or company_profile, so it stops short of a 5.

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 no when-to-use or when-not-to-use guidance and no named alternative. An agent must infer from the purpose sentence alone that this is the tool for UK financial-regulator authorisation checks, and must guess whether it also covers e.g. company-house style lookups.

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