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

Annotations already cover the safety profile (readOnly, openWorld, non-idempotent), and the description adds genuinely useful context beyond them: x402/prepaid payment pricing, the free trial, and the 'no personal data' scope limit. It does not describe rate limits or error behavior, so not 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?

Purpose is front-loaded and every clause carries information (modes, output fields, pricing). It is a single dense run-on sentence with heavy parenthetical nesting, which slightly hurts scanability.

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?

Despite an output schema already documenting returns, the definition still rounds out what an agent needs: both invocation modes, pricing/billing mechanics, trial availability, and the personal-data boundary. Nothing material for correct invocation is missing.

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 real meaning by mapping each parameter to a distinct outcome -- q yields a search, number yields the full profile with the enumerated fields. That distinction is not visible from the schema alone.

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 ('UK company check from Companies House') and distinguishes its two operating modes: a name search via q versus a full profile via number. It does not name or contrast with nearby siblings such as company-profile or company-report, so it falls 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?

Clearly tells the agent how to drive each entry point -- use q for a name lookup, or number for the full profile -- and gives a concrete example (00445790). It offers no when-not guidance or explicit alternatives, keeping it below a 5.

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