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

Beyond the readOnly/idempotent annotations, it discloses the exact return contract (valid:true with issuer, product id, passportVersion, validFrom; valid:false with reason strings such as 'revoked by the issuer'), the precise semantics of a valid result, the important limitation that validity does not imply latest version, and that no API key is required. These are exactly the behavioral facts annotations cannot express.

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 definition is front-loaded with the action and result shape, and the caveat about version staleness plus the no-API-key note are placed where they matter. It is somewhat long and repeats 'Aeroz' several times, but every sentence carries actionable information.

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 fully compensates by describing both success and failure payloads, the failure reason categories, and the authentication expectation. An agent has everything needed to call it and interpret the result.

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% and the single 'jwt' parameter is already documented as 'the compact vc+jwt credential'. The description adds only the origin constraint ('issued by Aeroz'), which is marginal beyond the schema, 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 description states a specific verb+resource ('Check a passport credential ... against Aeroz's published signing keys') and scopes it to vc+jwt credentials issued by Aeroz, which clearly separates it from siblings like verify_chip and get_passport. An agent can tell exactly what operation is performed without opening the 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?

It gives clear context (verifying a credential's signature/revocation status) and names the alternative for a related need: 'compare passportVersion with get_passport'. However, it never states when not to use this tool or how it relates to verify_chip, so it stops short of full when/when-not routing.

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