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

With no annotations, the description carries the full burden, and it does disclose the single most important non-obvious trait: the tool does not serve data and calling it has a side effect (recording a requirement). That is exactly the kind of gotcha an agent would otherwise misread as a data lookup. It stops short of describing the response payload or whether repeated calls are deduplicated, which keeps it from a 5.

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?

Two short sentences with zero filler, and the unusable status is placed early. Nothing repeats or pads the definition.

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 one-parameter probe with no output schema, the description covers the essentials an agent needs: domain, unavailability, and the recording side effect. A note on what the call returns (confirmation versus empty result) would close the remaining gap.

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?

There is one required parameter and schema description coverage is 100%, so the baseline is 3. The description adds no meaning beyond the schema for company_number — no format, jurisdiction, or identifier-scheme guidance beyond the loose 'UK company' framing.

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 identifies the domain resource (outstanding charges and security for a UK company) but immediately reframes the tool as a 'roadmap probe, not yet served', so the effective purpose is ambiguous: it does not fetch charges, it records a requirement. The final clause 'Calling records the requirement' is the only thing that tells an agent what the call actually accomplishes, and it arrives after the misleading domain framing.

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?

'Not yet served' implicitly warns an agent not to rely on this for real charge data, which is a useful negative signal. However, no alternative is named despite siblings like request_data, find_capability, and registry_doc_fetch that plausibly cover this need, and there is no statement of when an agent should deliberately call this probe versus skip it.

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