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

Annotations only declare readOnlyHint=true and openWorldHint=true, so the description must carry the rest and does: it discloses that values carry confidence and source evidence, that freshness is reported, and that unknown data is returned explicitly rather than invented. That integrity guarantee is genuinely useful behavior an agent cannot infer from annotations. It omits any rate-limit or latency context (fair-use limits surface only in the schema's tier text).

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 tightly written sentences, front-loaded with the purpose, then return contents, then the data-integrity guarantee. No filler or restatement of the tool name.

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 compensates by enumerating the returned payload (attribute values, resolved knowledge, signals, events, provenance, freshness) and the confidence/evidence contract. Payment and tier behavior are thoroughly covered in the schema. Only minor gaps remain, such as response size or latency expectations for the intelligence tier.

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%: organisation_number's pattern/format and tier's enum values, pricing, and x402 payment retry flow are all fully documented in the schema. The description adds only the phrase 'by organisation number', which the schema already covers. Baseline 3 is appropriate when the schema does the heavy lifting.

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 ('Retrieve'), resource ('machine-readable intelligence'), and access key ('by organisation number'), which clearly frames this as a single-company exact-identifier lookup. It never names a sibling, so the distinction from batch_get_companies, get_company_history, or search_companies is left to inference from 'by organisation number'. Clear, but no explicit sibling differentiation.

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?

Usage is implied rather than stated: the phrase 'by organisation number' signals that this is the exact-identifier path versus the search_* tools, but no when-to-use/when-not guidance or named alternatives appear in the description. The tier selection logic that would be the most useful usage guidance lives in the schema, not the description.

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