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

The description adds significant behavioral context beyond annotations: it states it is read-only and spends no quota (consistent with readOnlyHint=true), it specifies that signing secrets are never returned, and it describes the response fields including the meaning of lastStatus (HTTP code indicating broken endpoints). This level of detail helps the agent understand exactly what the tool does and does not expose.

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 three sentences long, each earning its place. The first sentence states the purpose and the key output (id). The second details the response fields and a critical insight about lastStatus. The third clarifies what is not returned and confirms read-only/no quota. No fluff, front-loaded, and well 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 no parameters, rich annotations, and no output schema, the description is remarkably complete. It explains the purpose, the returned fields (url, events, enabled, lastDeliveryAt, lastStatus), the meaning of lastStatus, and the absence of signing secrets. The agent can fully understand the tool's behavior and output without needing additional documentation.

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, so schema coverage is 100% trivially. According to guidelines, the baseline is 4 for zero-parameter tools. The description adds no parameter information because there are none, and that 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 clearly states the tool lists webhook endpoints on the account and provides the id needed to test one. It distinguishes from siblings like create_webhook (which returns signing secrets) and test_webhook (which uses the id). The verb 'list' and resource 'webhook endpoints' are specific and unambiguous.

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 explains when to use this tool (to list webhooks, get the id to test one, check for broken endpoints via lastStatus). It also clarifies what it does not return (signing secrets, which are only from create_webhook). While it does not explicitly state 'do not use this to create/delete', the annotations and context make that clear. The guidance is strong but not exhaustive.

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