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

Beyond the annotations, it discloses that a decision is persisted on the account (explaining why readOnlyHint=false and idempotentHint=false), that key binding imposes a signature requirement, and explicitly bounds the side effects: trusted raises search allowance but never changes prices or the owner's card requirement. That kind of non-obvious state-change and safety disclosure is exactly what annotations cannot convey.

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?

Four sentences, each carrying distinct content: identity framing, acquisition instructions, a signing caveat, and effect disclosure. The endpoint URL and audience are embedded inline rather than set off, which makes the middle slightly dense, but nothing is redundant.

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?

An output schema exists, so return values need not be explained, and the description fully covers the acquisition, transport, and effect path for a one-optional-param tool. The remaining omission is failure behavior, such as how an invalid, expired, or unsigned attestation is reported, which an agent may want before calling.

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, and the description adds real value on top: it identifies the header-based alternative transport that explains why the attestation parameter is optional, and names the token type (kya+jwt) via the schema. The only gap is that it does not describe the string format or validation requirements for the value itself.

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 second sentence states a concrete action and resource: obtain a KYA attestation from apis.io and pass it in, either as the parameter or via the APIs-IO-Attestation header. The opening line 'Show Yawplet who you are' is a hook rather than a specification, but the body makes the purpose unambiguous. No sibling tool is named, though none of the listed siblings is adjacent enough to require differentiation.

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 gives the prerequisites needed to invoke correctly: fetch the attestation from the apis.io endpoint with the correct audience, and note that a key-bound attestation only counts if the MCP request is Web Bot Auth-signed with that key. It also implies the payoff ('trusted raises the free search allowance'), which motivates when to call it. It does not give any explicit when-not-to-use case or say what to do if you have no attestation yet, so it stops short of a 5.

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