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

No annotations are provided, so the description carries full burden. It discloses pricing ($0.01 per call), payment method (USDC on Base mainnet), data source (official register), and return fields (status, type, incorporation date, etc.). It is a read-only operation, which is implied but not explicitly stated as non-destructive.

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 long but well-structured: it starts with the core purpose, then details capabilities, pricing, and target users. Each sentence adds information, though some repetition (e.g., 'Official UK register coverage' appears twice) slightly reduces conciseness.

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 having no output schema, the description thoroughly lists return fields (status, type, incorporation date, registered office address, SIC codes, insolvency history, officers with ECCTA identity verification). It also covers pricing, use case, and input examples, making it self-sufficient for an agent to understand the tool's behavior and output.

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%, but the description adds value by providing concrete examples ('Tesco', '00445790') and explaining the distinct role of company_number for detailed profiles. This goes beyond the schema's terse descriptions.

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 clearly states the tool searches the official UK Companies House register with two distinct operations: search by name/number or fetch detailed profile. It specifies the resource (UK Companies House register) and actions (search, fetch), distinguishing it from sibling tools that cover different domains.

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 explicitly states the use case: 'For KYB, AML and supplier due-diligence agents.' It provides examples of when to search vs. fetch profile. However, it does not mention when not to use or alternative tools, but the context is sufficient for an agent.

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