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

Annotations already cover the safety profile (readOnly, idempotent, openWorld, non-destructive), yet the description still adds real behavioral context: no authentication required, the key algorithms returned, and crucially the failure semantics ('an unknown kid is unverifiable, not refuted'). That last point is a genuine behavioral disclosure an agent cannot get from the 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?

Three dense sentences, each earning its place: what is returned, what it is for, and how to consume it safely. The most important content (what the tool returns) is front-loaded, and nothing is padded.

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 input parameters and no output schema, the description carries the full burden and does so: it describes the return structure (key types, kids, AKP entries), the verification use case, the matching rule, and the no-auth requirement. Nothing an agent needs to call or interpret this tool is missing.

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?

The tool takes zero parameters, so per the baseline this scores 4. The description adds nothing about parameters because there are none to describe, and it correctly directs the agent to match on the kid in the response rather than any input.

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 ('Get InsumerAPI's public signing keys as a JWKS') and names the exact contents (ECDSA P-256 key, ML-DSA-65 post-quantum key as RFC 9964 AKP entries). An agent can immediately distinguish this from the attestation/trust siblings, which consume these keys rather than expose them.

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 the context in which the keys matter ('signatures on attestation and trust responses verify against these keys') and gives a concrete consumption rule ('match an entry by the kid, never by position'). It does not name a sibling alternative or an explicit when-not condition, but the usage context is unambiguous.

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