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

With no annotations, the description carries full behavioral burden and does so thoroughly. It discloses that the signing secret is shown only once, details the exact verification request (POST, headers, body) and timing constraints, notes the permission scope, and warns about side effects of re-registration (old secret stops working) and daily verification limits. This goes far beyond a typical vague description.

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 long but every sentence carries critical information; it is dense rather than verbose. The most time-sensitive instruction (store the secret) is front-loaded, and the rest follows a logical order: verification steps, timing, restrictions, re-registration effects, and limits. Slight redundancy (e.g., 'https://' repeated) but overall appropriate for a complex operation.

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 and no annotations, the description covers the essential behavioral context: verification protocol, timing, side effects, and allowances. It does not explicitly describe the registration response structure, but it conveys the challenge and secret concept sufficiently for an agent to understand the next steps. The description is complete enough for correct invocation.

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 does not add much beyond the schema's 'The https:// URL you control'—it repeats that the URL must be https and controlled, but does not introduce additional constraints, formats, or examples. It effectively documents the single parameter adequately via the schema, and the description adds negligible extra semantic value.

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 precisely states the tool's purpose: to register an https:// URL as a delivery destination. It clearly distinguishes from siblings like verify_destination and delete_destination by explaining the registration flow (challenge and signing secret) and the verification step. The phrasing 'Claim an https:// URL you control' is a specific verb+resource that leaves no ambiguity.

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 conveys when to use this tool (to register a new destination) and implicitly when not to (e.g., to verify, use the separate verify step). It gives explicit conditions like 'within 15 minutes' and 'a fixed-response webhook cannot pass,' which guide correct usage. It does not explicitly name sibling tools, but the context signals the differentiation.

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