Verify a cosign signature

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

The description adds significant behavioral context beyond the annotations: it shells out to an external binary, contacts the registry and transparency log, may return an EP_EXTERNAL_TOOL error, and explains the optional keyless parameters. This is exactly the kind of disclosure that helps an agent anticipate side effects and failure modes.

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 well-structured and efficient: a one-sentence purpose, a bolded external-system warning, and a concise Args list. Every sentence carries meaningful information with no redundancy or 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?

Given the tool's complexity, the description covers the key operational aspects: external dependency, PATH requirement, error code, keyless mode, and all parameters. The output schema likely handles return-value details, so no additional output documentation is needed here.

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. The description adds meaning by explaining that certificate_identity and certificate_oidc_issuer are only needed for keyless verification, clarifying their role in context. This goes slightly beyond the schema's individual field descriptions.

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 clearly states the tool verifies a container image signature with `cosign`, using a specific verb and resource. This distinguishes it from sibling tools like `verify_pack_signature` and `verify_slsa_provenance`, which target different artifact types.

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?

The description gives clear context for use: verify a container image signature via cosign, with keyless verification enabled by supplying certificate identity and OIDC issuer. It notes the prerequisite of cosign being on PATH, but does not explicitly state when not to use the tool or name alternatives.

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