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

Beyond the readOnlyHint/openWorldHint annotations, it discloses price ($0.01), a hard rate limit (3 non-matching answers per credential stop checks), a privacy guarantee (CPF never stored, published, or revealed), a side effect (the person sees every check), and the match return (a verifier-specific subject_ref). This is rich operational context an agent cannot get from structured fields.

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?

Dense but front-loaded: cost and scope lead, then match output, then privacy/limit/notification constraints. Every clause carries information. Slightly marred by the clipped fragment 'On a match, a subject_ref of your own for that person', which reads as a sentence stub.

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 states the return value (subject_ref on match) and covers cost, rate-limiting, privacy, and notification. For a simple two-parameter paid check, this is close to complete; only the non-match return shape is left implicit.

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%, so both cpf and credential_id are already documented in the schema (cpf used for comparison only, credential_id returned by kya_register). The description reinforces the CPF's comparison-only/never-stored role but adds no syntax or format detail beyond the schema. 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 description names a specific operation and resource: a signed yes/no answer on whether a supplied CPF matches the e-CPF holder behind a credential, scoped to a person's agent (principal.kind person). This is clearly distinguishable from prove/verify siblings. It stops short of explicitly naming which sibling to prefer, but the matching semantics are concrete.

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?

It implies the scenario (you already hold a CPF and want to check it against the e-CPF holder) and names the scope (person-kind principal), but gives no explicit when-to-use/when-not guidance or named alternatives among the many kya_* siblings. Usage is inferable rather than stated.

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