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

Annotations already cover the read-only, idempotent, non-destructive profile, and the description adds genuinely useful context beyond them: the authoritative-registry caveat, the explicit 'not independent beneficial-ownership verification' disclaimer, pre-payment rejection of unsupported capabilities, and the x402 USDC price. It stops short of describing pagination or response shape, but the safety and cost profile are clear.

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?

Four sentences, each carrying distinct information (capability, coverage caveat, rejection behavior, price), with the capability and scope front-loaded. The pricing sentence is slightly dense but is necessary operational context for a paid endpoint.

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 a simple single-parameter read with an output schema, so return values need not be explained. The description supplies the regulatory caveat, geographic coverage, payment model, and failure behavior, leaving little an agent needs that is missing.

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?

With a single parameter at 100% schema description coverage, the schema already explains that entity_id is a stable ID from search_company to be passed unchanged. The description's phrase 'resolved legal entity' reinforces that prerequisite but adds no new syntax or format detail, 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 opens with a specific verb and resource ('Retrieve normalized ownership or control records for a resolved legal entity'), which is far more informative than the bare tool name. It scopes the data to GB Companies House PSC records, though it never explicitly contrasts itself with the sibling get_company_owners, leaving the entity-vs-company distinction to inference.

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?

Coverage limits ('GB Companies House PSC records only') and the statement that unsupported capabilities are rejected before payment give an implicit when-to-use and when-not-to-use signal. However, no alternative sibling is named for cases outside GB PSC coverage, and the dependency on a prior search_company resolution is only conveyed via the schema.

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