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

Goes well beyond the annotations by disclosing that the HMAC signing secret is returned only once and cannot be re-read, the exact signature header format and HMAC construction, at-least-once delivery semantics, and dedupe-by-event-id. These are exactly the operational facts an agent needs and none are recoverable from the annotations or schema.

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 short sentences, front-loaded with the action and its constraint. The HMAC formula is dense but is the highest-value content in the definition and would be costly to omit.

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 carries the return-value burden and covers the critical one-time secret, but does not mention that the response also yields an identifier needed for later get_webhook/delete_webhook/test_webhook calls. Auth or scope requirements for registering a webhook are also unstated.

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 the baseline is 3. The description still adds value by stating the omit-means-all default for event_types and pointing at list_webhooks as the source of valid values, though it does not restate the url format beyond what the schema already says.

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 constraint that the endpoint must be public https. This clearly separates it from the read/verify siblings list_webhooks, get_webhook, test_webhook and delete_webhook.

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?

'Omit event_types to receive everything' gives concrete guidance on the optional parameter's default behavior, and the reference to 'the catalog from list_webhooks' routes the agent to the right sibling for discovery. It stops short of explicit when-not-to-use guidance, e.g. telling the agent to follow up with test_webhook to verify delivery.

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