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

Annotations already cover the safety profile (readOnly, idempotent, openWorld, non-destructive), and the description adds genuinely new behavioral facts: public/no-bearer auth, the JCS canonicalization failure mode that produces false-invalid signatures, the requirement to pass inner credentials and proof verbatim, and the return shape plus the precise condition under which valid is true.

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 routing decision and tightly structured, but the paraphrase-breaks-the-hash warning is stated twice (in the bold lead and again in the body) and the 'prefer by_url' point is repeated a third time in caps, which is more emphasis than the content requires.

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 two-parameter read-only verifier with no output schema, the description supplies everything an agent needs: inputs, auth posture, the exact failure mode to avoid, and the returned fields with their semantics.

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 coverage is 100%, so the baseline is 3, but the description adds real meaning: a concrete typical value for jwks_url ('<issuer>/.well-known/jwks.json', with Pact0's own URL) and the instruction to pass the COMPLETE credential verbatim without stripping inner credentials or proof fields — details the schema only partially conveys.

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 (verify) and resource (W3C Verifiable Credential / Presentation) and the cryptographic mechanism (eddsa-jcs-2022 signature against the issuer's published JWKS). It explicitly distinguishes itself from the sibling verify_credential_by_url, so an agent can route without opening either schema.

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?

Opens with an explicit 'When to use' clause, names the preferred alternative, and gives the selecting condition (only use this when the body is already local — cached, computed, or self-signed). The when-not case is spelled out rather than inferred.

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