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

With no annotations, the description carries the burden and discloses the verification behavior: checks signature, kid, and tampering, and is free. It also mentions cross-checking the kid against a public key endpoint. It doesn't explicitly state non-destructiveness or return format, but the disclosed verification steps are substantive.

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 description is front-loaded with the core purpose and is relatively compact. It's slightly redundant with 'FREE' and '(price: $0 USDC, tier: free)' appearing twice, and includes a promotional sentence. Still, it earns its place overall with no fluff.

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 tool with no output schema, the description covers input format, verification checks, and additional cross-check guidance. It doesn't provide an example or error handling, but it's sufficient for an agent to know what to supply and what to expect.

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% for the single payload parameter, and the schema already describes it as including the onyx_attestation block. The description reinforces the input format but adds little beyond the schema—only the verification context. Baseline 3 is appropriate.

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 uses a specific verb+resource: 'Verify an Onyx-signed security verdict' and details the exact verification checks (Ed25519 signature validity, kid, tampering). This clearly distinguishes it from sibling verification tools like onyx_agent_verify or onyx_verify_explain by focusing on cryptographic attestation verification.

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 states when to use: 'Paste back any result from an Onyx tool' and explains the benefit of independent verifiability. It provides a concrete cross-check action against /.well-known/onyx-pubkey. However, it doesn't explicitly name alternatives or exclusions, so it lacks full comparative guidance.

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