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

Adds substantial behavior beyond the annotations: a one-hour expiry on the challenge, a required publish step at an HTTPS well-known URL, a secrecy constraint on the requester key, a scan prerequisite, and two explicit scope boundaries (no payment/target credentials sent, never signs payments). This is exactly the kind of context annotations like readOnlyHint=false and idempotentHint=false 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?

Six short sentences, front-loaded with the core action, expiry, and the publish instruction. Slight redundancy: secrecy of the requester key is stated twice ('your private ... key' plus 'Keep the requester key private'), and the two payment/credentials sentences overlap.

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 output schema, the description compensates by telling the agent what to do with the return value (publish the returned JSON at its well-known URL) and what the prerequisites are. It does not describe the JSON's shape, which is a minor gap since the agent must publish it verbatim.

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 0%, so the description has to carry the load. It explains requester_key well ('private random 32-byte ... in lowercase hex' explains the ^[a-f0-9]{64}$ pattern), but 'origin' is only indirectly implied by 'domain challenge' and its URI format is never elaborated.

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+resource: 'Start a one-hour domain challenge' bound to a requester key, which is clearly distinct from confirm_ownership_proof and scan_origin. It never names the sibling it hands off to, so differentiation is inferable rather than explicit.

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?

'A completed scan is required before confirmation' implies the ordering with confirm_ownership_proof and the existence of a follow-up step, but the alternative tool is never named and there is no when-not-to-use guidance. Usage is implied rather than spelled out.

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