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

With no annotations, the description carries the full burden and does well: it discloses the data source behavior ('official API with public fallback'), the red-flag logic applied (overdue, dissolved, officer churn, mass-formation office), and the price. It stops short of stating auth requirements, failure modes for ambiguous name matches, or result completeness, which 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 scope, then the alternative and cost, then an example — a sensible ordering with little waste. The cost figures and example are tightly packed into the same sentence, which makes it denser than ideal but not padded.

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?

For a two-parameter, no-output-schema tool it covers purpose, the content of the result, the cheaper alternative, and pricing. The only material gap is the input constraint ambiguity (no parameter required, no name-matching semantics) given there is no schema documentation to fall back on.

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% and neither parameter is marked required, so the description must clarify usage. It does convey that lookup accepts 'number or name' and gives a concrete example ({number:"00445790"}), but it never says whether one is required, whether both may be combined, or how partial name matching behaves.

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 UK Companies House due diligence') and enumerates the returned sections (profile, officers, PSCs, filings, charges, insolvency, red flags), so an agent knows exactly what this produces. It also explicitly separates itself from the sibling uk_company_lite.

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?

Names the alternative (uk_company_lite) and the exact condition that selects it ('status/flags only'), with a concrete cost trade-off ($0.05 vs $0.50). Nothing about when to prefer which tool is left to inference.

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