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

Annotations already declare readOnly, idempotent, non-destructive and open-world, so the safety profile is covered. The description adds genuinely non-schema context: the call is paid ($0.0053 production USDC via x402 on Base mainnet), which an agent must know before invoking it, and that it requires an already-known company number. It does not say what happens on an unknown/invalid registration, but the payment disclosure is a substantial addition.

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?

Three sentences, front-loaded with the core action and resource, followed by scope enumeration then use cases then cost. The field list is long but informative; the price sentence earns its place because it affects invocation decisions. Slight bloat from the unfocused use-case sentence.

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?

The tool is simple (one required parameter, no nesting), an output schema exists so return shapes need not be explained, and the description covers purpose, scope, prerequisites and payment. The main remaining gap is routing guidance among the many sibling lookup tools, which for a registry with both company- and entity-level variants would be valuable.

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%: the single parameter has a pattern, a format note, an example and a pointer to search_company. The description only reinforces 'known UK company number' as a prerequisite, adding little beyond the schema, so the baseline of 3 applies.

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 uses a specific verb ('Retrieve') and resource ('Companies House profile for a known UK company number') and enumerates the payload (legal name, status, type, incorporation date, registered office, SIC codes, accounts/confirmation metadata). The field list implicitly separates it from siblings like get_company_officers, get_company_filings and get_company_insolvency, but it never explicitly names those alternatives or the near-twin get_entity_profile, so the differentiation is inferred rather than stated.

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?

It lists use cases (public-register verification, onboarding, supplier checks, corporate research) but these describe business scenarios rather than tool-selection criteria. There is no when-not-to-use guidance and nothing explaining when to pick get_company_profile over get_entity_profile or why the company must already be 'known' (i.e., obtained via search_company).

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