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

Goes well beyond the annotations: discloses 24-hour caching, Blind Mode semantics (officers and individual PSCs are never ingested; filing events carry category codes not names), per-call credit cost, the no-key preview cap and 20 calls/day limit. These are non-obvious behaviours an agent cannot get from readOnlyHint/idempotentHint.

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 the core purpose, then the returned fields, then safety/cost constraints; every sentence carries information. The field enumeration and pricing sentence are dense 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 read-only lookup with no output schema, the description thoroughly characterises the payload, privacy behaviour, cost model and rate limits. Its only real gap is the three uninterpreted parameters, which the schema also fails to explain.

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 0% across 5 parameters, yet the description only clarifies the single-record key form for company_number and company (e.g. {"company_number":"00000006"}). The q, page and per_page parameters go completely undocumented, and page/per_page sit oddly against 'One record per call,' leaving the agent to guess how they interact.

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 ('One UK company by number or name, live from the official Companies House API') and enumerates exactly what the profile contains (status, SIC codes, charges, filing events, PSCs). The phrase 'One record per call' separates it from the plural list sibling query_uk_companies.

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?

Gives usable lookup context ('by number or name', named-key example with company_number) and operational context (24h cache, 1 credit, preview limits without a key), but never states when to prefer this over the neighbouring query_uk_companies or the other UK source tools. Usage is implied rather than prescribed.

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