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

Annotations declare a non-read-only, non-destructive mutation; the description adds real value by disclosing that payloads are HMAC-signed and that the call returns a webhook ID and secret. It does not say whether the secret is shown only once, how to rotate it, or what happens to duplicate registrations.

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 tight sentences: purpose first, security/behavior second, return value last. Nothing is wasted and nothing is buried.

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?

A four-parameter mutation with full schema coverage and annotations; the description usefully covers the return value even though no output schema exists. Minor gaps remain around secret lifecycle and duplicate registration, but the essentials for correct invocation are present.

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 url, events, secret and apiKey are already fully documented with formats and constraints. The description only echoes the event examples and the HMAC/secret concept, adding no syntax or constraint detail beyond the schema.

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 and resource ("Register a webhook endpoint") plus the concrete effect (real-time HTTP POST notifications) and gives representative event names. It is unmistakably different from list_webhooks or delete_webhook by implication, but never names those siblings explicitly.

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 — call this when you want event notifications delivered to an endpoint — but there is no explicit when-to-use/when-not framing, no mention of using list_webhooks to inspect existing registrations, and no guidance on whether re-registering a URL is allowed.

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