Register a webhook endpoint. The signing secret is returned only in this response.

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

The description adds substantial behavior beyond the annotations: public reachability is required, HTTPS is mandatory in live mode, private network addresses are refused, and the signing secret appears only in the creation response. It also explains how the secret is used, discloses the 16-endpoint-per-mode limit, and supplies the exact quota error.

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 important operational constraints are front-loaded and expressed compactly. Repeating the title's opening and then restating the one-time-secret warning introduces noticeable redundancy, preventing a perfect conciseness score.

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?

Despite the absence of an output schema, the description discloses the most important response behavior: the `whsec_…` secret is available only once and must be stored for signature verification. Combined with the schema, it covers required inputs, event selection, idempotent retries, endpoint validation, limits, and a relevant failure mode, which is sufficient for correct invocation and result handling.

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?

With only 25% schema description coverage, the description compensates well by explaining the reachability and protocol constraints on `url` and the wildcard behavior of `enabled_events`. Together with the schema's event enum and idempotency-key documentation, this gives the agent enough meaning to populate all consequential parameters correctly.

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 clearly states the verb and resource: registering a publicly reachable webhook endpoint to receive subscribed events. It does not explicitly contrast creation with siblings such as update_webhook_endpoint, test_webhook_endpoint, or rotate_webhook_secret, so sibling differentiation remains implicit.

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 provides clear usage context: create an endpoint to receive either selected events or all events using `*`. However, it gives no explicit when-not guidance or alternatives, such as updating an existing endpoint or rotating the secret of one already created.

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