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

Beyond the annotations (readOnlyHint=false, destructiveHint=true, idempotentHint=false, openWorldHint=true), the description discloses genuinely valuable behavior: the HMAC secret is returned only once, deliveries are best-effort with up to 3 attempts, and private/internal/localhost targets are rejected. These are non-obvious operational facts an agent could not infer from the 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?

The purpose is front-loaded and the body is dense with specific facts (limits, security rejects, retry count) rather than filler. The "Inputs: url, optional events, and token" clause is mild redundancy against a 100%-documented schema, keeping it just under a 5.

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 steps in and states what comes back (webhook id and one-time HMAC secret), and it covers quotas, target restrictions, and delivery guarantees. An agent has everything needed to call this correctly and to set expectations about the response.

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%, and the schema documents url constraints, the token fallback via Authorization header, and the event enum more precisely than the description does. The description's "Inputs: url, optional events, and token" largely restates the schema, so the baseline 3 is appropriate.

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 opens with a precise verb+resource ("Registers an http or https URL") and enumerates the exact event types the webhook subscribes to, so the agent knows exactly what this tool creates. It does not explicitly name or contrast with the sibling webhooks tools (list_webhooks, delete_webhook), so it falls one notch short of full sibling 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 real selection context: tier quotas (Free 1, Hobby 5, Pro 20), the rejection of private/internal/localhost targets, and delivery semantics, all of which inform whether the call is appropriate. It stops short of naming alternatives such as list_webhooks or delete_webhook for managing webhooks afterwards, so usage guidance is clear but not bounded by explicit exclusions.

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