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

With no annotations, the description carries the full burden and does so well: it names the signature algorithm (Ed25519), the signed payload (request hash, result, sources, timestamp, PG1 version), and where the signature lives per transport (MCP _meta, A2A metadata, REST field). It also discloses cost ('Always free') and that verification can be done offline. The only gap is the shape/semantics of the verification outcome, which is neither described nor provided by an output schema.

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?

Purpose is front-loaded in the first sentence, followed by the signature scheme, the per-transport signature locations, the input instructions, and the key/offline note. Four dense sentences, all earning their place, though the transport-location and key-URL details could be pushed to linked docs without losing meaning.

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 read-only verification tool with a fully documented 2-required/2-optional parameter set, the description covers inputs, signature provenance, key retrieval and an offline alternative. With no output schema, it leaves the verification response format (pass/fail, error reasons) unstated, which is the one meaningful omission.

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 genuine meaning: it explains that passing tool and arguments binds the check to a specific request hash ('to check it answers that exact request'), and that the result's own signature field is ignored in favor of the supplied block. That is more than the schema's terse 'Optional: the tool that was called.'

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 (verifies) and resource (a PG1 result's authenticity/integrity) with the scope spelled out: 'really came from PG1, unchanged'. No sibling tool in the list performs signature verification, so it is unambiguously distinguishable from check_*/get_* tools.

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?

Explains exactly what to pass (the result object and signature block, optionally tool and arguments to bind the result to a specific request) and notes the alternative path: 'you can verify offline without this tool' with the JWKS URL. It stops short of stating when verification is required versus optional, so it is clear context rather than an explicit when/when-not rule.

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