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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds genuinely new behavioral context — the 1-credit cost and the specific contents of the response — which the annotations do not convey.

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 tightly written sentences plus a parenthetical cost note. The identifier and scope come first, then the return payload, then the use case — no filler anywhere.

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 no output schema, the description usefully enumerates what comes back, which is the main completeness burden here. It omits only edge-case behavior, such as what happens when the IRN is unknown or the person has no disciplinary record.

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% and the single parameter already documents its type and an example format ('ABC01234'). The description reinforces that this is an individual reference number but adds no syntax, validation, or lookup-failure detail beyond the schema.

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 ('FCA register check on a person'), the exact key it takes ('individual reference number'), and enumerates the returned data: approval status, current/past regulated roles, firms, and disciplinary history. The person-level scope inherently separates it from fca_firm and fca_search.

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?

'Use to check a financial adviser, mortgage broker or senior manager' gives clear when-to-use context by naming the subject types. It stops short of explicit routing guidance, such as using fca_search when only a name is known rather than an IRN.

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