Verify a credential's signature (offline)

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

With readOnlyHint/openWorldHint already covering the safety profile, the description adds the non-obvious behavior: the issuer key comes from /.well-known/kya.json and is 'fetched once', and a post-issuance revocation cannot be seen, leaving live_status unknown. That limitation disclosure is exactly the kind of context the name ('offline') would otherwise mislead on.

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?

Three short sentences with the cost note ('Free.') and the scope front-loaded, followed by the limitation and the routing pointer. No filler.

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 single-parameter verification tool with no output schema and strong annotations, the description covers cost, scope, mechanics and the key limitation. It stops short of indicating the shape of the verification result (beyond hinting that live_status is a field), which leaves the return contract 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?

Only one parameter and the schema describes it at 100% coverage ('the full credential JSON, including its attestation'), so the schema does the heavy lifting. The description adds the notion that the caller must already hold the document, but no syntax or shape detail beyond the schema — baseline 3.

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 and resource ('Checks a credential document you already hold') plus exactly which checks are performed: the issuer's Ed25519 signature and the expiry. It explicitly separates itself from the sibling kya_verify, so an agent can pick between them 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?

Gives the selecting condition for this tool (a credential document you already hold) and names the alternative with its trigger ('use kya_verify for the live status'). It also flags the revocation blind spot as a reason the alternative may be required.

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