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

Annotations only signal that this is a mutating, non-idempotent call; the description adds substantial behavioral detail beyond that. It reveals that signingSecret is shown only once and cannot be retrieved later, explains receiver verification via HMAC-SHA256 with timestamp rejection, and clarifies global vs. resource-scoped event validity.

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 dense but every sentence earns its place: the one-time secret warning, verification mechanics, the global-vs-scoped event caveat, and the documentation pointer. The core action is front-loaded, and the critical constraints are prominently marked.

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 an 8-parameter tool with an output schema and nested options, this description is complete: it covers the one-time secret, verification requirements, valid event scoping, the sibling subscription path, and a documentation fallback. An agent has everything needed to call it correctly.

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 each parameter already has a detailed description including the enabledEvents restriction, environment grant requirement, and advancedOptions shape. The description reinforces the enabledEvents constraint but does not define new parameter semantics beyond what the schema already provides, so the high-coverage baseline of 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 specific verb and resource: 'Register an HTTPS URL to receive Extend events (webhooks group).' It also distinguishes itself from create_webhook_subscription by explaining that resource-run events belong on the subscription tool, so an agent can tell them apart without opening the schema.

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 explicit when-not-to-use guidance: resource-run events such as workflow_run.completed are rejected here and must be scoped via create_webhook_subscription. It even prescribes the correct sequence (create endpoint with enabledEvents [] then subscribe) and suggests calling get_documentation first for manual setup.

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