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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds genuinely non-structured context: a cost of 2 credits (important for an agent deciding whether to call) and the scope of the record returned, including enforcement/clone risk. It does not discuss failure modes (no match, ambiguous name) or response shape, keeping it out of the 5 band.

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 the verb and resource, followed by a compact enumeration of returned fields, then usage and cost. The field list is long but each item is substantive; the only slight redundancy is repeating the identifier options already in the schema.

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 correctly compensates by listing what is returned, and it discloses the credit cost and intended decision context. The remaining gap is behavior on name-based lookups — whether multiple firms may match and how ambiguity is handled — which matters for a tool where both identifiers are optional.

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%, with the schema itself stating that name is "used if no frn", so the precedence rule is already documented. The description restates the two identifier options but adds no format, validation, or disambiguation detail beyond the schema. Baseline 3 is appropriate when the schema carries this load.

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 ("Full FCA register check on a financial firm") plus the accepted identifiers (FRN or name), then enumerates exactly what is returned: authorisation status, permissions, trading names, addresses, complaints contact, regulators, client money, fines/enforcement. This makes it clearly distinguishable from the sibling fca_individual (people) and fca_search (lookup), and from the general kyb_check.

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?

Gives an explicit use case and audience: "Use before dealing with a bank, lender, broker, adviser, insurer or investment firm, and to spot cloned firms." That is concrete when-to-use guidance. It stops short of naming alternatives (e.g. "use fca_search first if you only have a name") or exclusions, so it falls just below the top band.

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