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

With no annotations, the description carries the full behavioral burden and does disclose a great deal: the verdict, the accountable party, the verbatim terms clause, the signup-door signals, and explicit null semantics ('Null means nobody there was asked, which is not a finding'). It also candidly flags data-reliability limits on the captcha readings. It omits auth/permission requirements and error behavior for unknown services.

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?

The first two sentences are front-loaded and effective, but the bulk of the text is statistical minutiae about captcha re-read disagreements across 54 doors ('10 understated it, 5 named a widget the page lacked, 1 changed type'). That level of provenance detail does not help an agent select or invoke the tool and buries the operative guidance.

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 must explain returns, and it does — verdict, accountable party, clause text, signup-door observations, and the answered_by field. A single-parameter lookup with this much return detail is adequately covered, though the deliverable is harder to parse than it needs to be.

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 a single parameter with 100% schema description coverage; the schema already documents case-insensitive substring matching. The description adds no additional meaning about how 'service' is resolved, so the baseline 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 opening sentence states a specific verb and object: 'Check whether a non-human actor may hold an account at a service.' That is unambiguous and actionable. It does not, however, distinguish itself from the sibling list_named_non_human_routes, so it lands at a solid 4 rather than a 5.

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?

'Call this BEFORE creating an account anywhere' is an explicit, well-placed when-to-use trigger that an agent can act on in a signup workflow. There is no statement of when NOT to use it and no routing to the sibling tool, so it stops short of a 5.

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