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

Annotations already declare readOnly, idempotent, non-destructive, open-world behavior, so the safety profile is covered. The description adds genuinely new behavioral context not in the annotations: the call is metered against a Stratum API balance and a test key option exists, which materially affects invocation decisions. It stops short of stating cost amount or any rate limits.

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 deliverable, followed by a compact parenthetical of contributing factors and a short billing note. Every sentence earns its place; the factor list is slightly dense but informative rather than wasteful.

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 usefully enumerates what the result contains (the score plus its contributing factors), which is the key thing an agent needs. It omits score scale/range and response shape, a minor but real gap for a tool whose output is its entire value.

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?

Single required parameter with 100% schema description coverage ('Companies House number'), so the schema already carries the semantics. The description adds nothing about the format or validation of companyNumber; baseline 3 applies 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 the specific resource ('a risk score for a UK company') and enumerates the factors it returns (overdue accounts, charges, officer turnover, insolvency history, age, status). This clearly separates it from siblings like company_profile or company_owners, which return raw data rather than a derived score, though the description never names those alternatives 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?

Usage is implied by the resource ('risk score for a UK company'), and the billing note nudges the agent to consider cost before calling. However, there is no explicit when-to-use/when-not guidance and no reference to the sibling tools that return overlapping company data.

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