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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, making the safety profile clear. The description adds context about the event types and explicitly says 'Read-only', which aligns with annotations. However, it does not disclose other behavioral details like pagination, ordering, or response structure (though output schema likely covers this). The added event-type context is useful but not behavioral beyond safety.

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 a single sentence with a colon and a parenthetical list of event types. It is front-loaded with the primary action ('List the webhooks registered for this user'). While the event enumeration is somewhat long, it is purposeful and not redundant. No wasted words, though the parentheticals add density. It earns a 4 for being appropriately sized and structured.

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?

Given the tool's low complexity (no parameters, simple list operation) and the presence of an output schema, the description need not explain return values. It fully covers the purpose, scope ('for this user'), and event types. There are no obvious gaps in what an agent needs to invoke it correctly: the read-only nature is stated and annotations confirm safety. Complete for a zero-parameter tool.

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?

The tool has zero parameters, and the schema coverage is trivially 100% (empty properties). Per the rubric, a zero-parameter tool gets a baseline of 4. The description adds no parameter information, which is correct since there are no parameters to explain. The description does not need to compensate for any schema gaps.

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 tool lists webhook endpoints registered for the user, using a specific verb ('List') and resource ('webhooks'). It enumerates the event types that trigger the webhooks, distinguishing this from sibling tools like create_webhook_endpoint or update_webhook_endpoint. The purpose is unambiguous and distinct from all 47 sibling tools.

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?

The description implies usage by stating 'List the webhooks registered for this user' but does not explicitly compare to alternatives or state when not to use it. There is no mention of why an agent might prefer this over other webhook-related tools (though no direct alternative exists for listing). The context is clear but exclusions are absent, so it falls at 'implied usage' rather than explicit guidance.

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