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

Annotations already declare readOnlyHint and openWorldHint, but the description adds genuinely useful context the annotations cannot carry: the exact return contents (birth month/year, appointment count, addresses, and full company lists for only the first few matches), plus the auth/payment model ($0.05 USDC per successful call via x402 on Base or Solana). This is meaningful disclosure for a paid, open-world lookup; only rate limits and the truncation reason for 'first few' are left implicit.

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 and output shape are front-loaded in the opening clause, and the pricing/auth note is correctly placed last. The middle portion is dense but every clause carries information; no filler sentences are present.

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?

With no output schema, the description fully carries the burden of explaining return values, and it does so at two levels of detail (summary fields and per-company appointment breakdown). Combined with the explicit payment requirement and the annotation-covered safety profile, an agent has everything needed to decide to call it and anticipate the result.

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% for the single required 'query' parameter, so the baseline is 3. The description goes beyond the schema by explaining the consequence of each input mode — a name yields all matching officer records, while an officer ID yields that record's appointments — adding behavioral meaning not present in the schema text.

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 ('Find a person on the Companies House register by name') and enumerates the record types returned (director, secretary, LLP member). It is distinguishable from the sibling uk_company_lookup by the person-centric framing, but the description never names or contrasts that sibling explicitly.

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 line 'An officer ID returns that record's appointments' clarifies the alternate input mode, implying when to pass an ID rather than a name. However, there is no explicit guidance on when to use this tool versus uk_company_lookup or us_company_lookup, and no stated exclusions or prerequisites beyond the payment note.

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