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

No annotations exist, so the description carries the full burden. It usefully discloses the billing trait ('1 point per returned record') and the shape of returned data (name, registration number, status, address, link), but omits any auth, rate-limit, or pagination behavior despite a start_page parameter.

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 front-loaded sentences with no filler: purpose first, then the cost note. Both sentences earn their place, though the returned-field list is slightly list-like.

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 keyword search tool with full schema coverage and no output schema, the description supplies the return fields and the cost model, which is most of what an agent needs. It leaves out how paging behaves across start_page, a minor gap.

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%, so every parameter is already documented in the schema (including the status enum and max_items default). The description adds only the 'by company name' framing for the required keyword, which is the baseline expectation when the schema does the heavy lifting.

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 (search) and resource (United Kingdom company registry / Companies House) scoped to company name, and enumerates returned fields. It separates itself from the family of other-country searches by naming the UK registry, but never distinguishes itself from its closest sibling run_uk_companies or run_uk_company_filings.

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?

'By company name' implies the tool is used when a company name is known, which is a mild usage signal. However, it never states when to prefer this over run_uk_companies or the other registry tools, and gives no exclusions — guidance is only implied.

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