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

The annotations already cover the safety profile (read-only, idempotent, non-destructive), so the description adds value by disclosing exactly which pieces of company data the call returns. It also communicates that the result is a composite profile rather than a single filing or charge record. No contradiction with annotations exists.

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?

The description is compact, front-loads the main purpose in the first sentence, and then adds only useful clarifying details. There is no repeated information from the tool name or title, and every sentence earns its place.

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 single-parameter, read-only lookup with a rich output schema, the description covers the tool's scope, return contents, and prerequisite workflow. Given the strong annotations and schema coverage, the agent has enough information to select and invoke the tool correctly.

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?

The input schema already extensively documents company_number, including format examples and the fact that it comes from company_search, so parameter coverage is effectively 100%. The description reinforces the use of company_search but does not add substantial new parameter meaning 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?

The description opens with a specific verb and resource ('Fetch the full Companies House profile for a company number') and then lists the concrete data returned (status, registered address, SIC codes, compliance flags, outstanding charges). This clearly distinguishes it from siblings like dd_company_charges, dd_company_filing_history, and dd_company_officers.

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?

The description gives a clear prerequisite: 'Use company_search first to find the company number.' This establishes the expected workflow. It does not explicitly mention when to prefer sibling tools such as dd_company_filing_history over this one, but the listed return fields and prerequisite provide adequate selection context.

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