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

Annotations only cover the safety profile (not read-only, not destructive, not idempotent, open-world), and the description goes well beyond them: the secret is returned once and never again, deliveries are at-least-once so consumers must dedupe by Webhook-Id, signature verification uses HMAC-SHA256 over timestamp plus raw body, and there is a hard cap of 10 endpoints. That is exactly the operational context an agent cannot get from structured fields.

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 with no filler; the what-is-it sentence leads, followed by the return value and the delivery contracts. It is information-heavy but front-loaded, with only minor compression loss from stacking signature, dedupe, and limit details together.

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 correctly carries the return-value burden by explaining the one-time secret, and it also covers verification procedure, delivery semantics, and the endpoint quota. An agent has everything needed to create the webhook and tell the user how to consume it.

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 100%, so both url and events are already documented, including an enum list and a typical event set example. The description adds the delivery payload shape ({id, type, created_at, data}) but nothing further about the two parameters themselves, so the baseline of 3 applies.

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?

"Registers a public HTTPS URL that receives a POST for each chosen event" is a specific verb+resource statement with the payload shape spelled out. It clearly conveys creation, but it never names update_webhook, list_webhooks, or rotate_webhook_secret as the alternatives, so sibling differentiation is inferred rather than stated.

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?

Usage is implied by "Registers" and the "Up to 10 endpoints" ceiling, which tells an agent this is the create path for a limited resource. There is no explicit when-to-use/when-not guidance or pointer to update_webhook for modifying an existing endpoint.

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