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

With no annotations, the description carries the disclosure burden and does so well: it establishes this is a scoped read, warns 'Never returns the signing secret' (a real expectation boundary), and notes the webhook may not exist ('if any'). It stops short of stating what is returned when no webhook is registered or any auth failure behavior.

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?

Front-loaded with the resource identity, followed by a compact field list that substitutes for the missing output schema, then a single diagnostic-use sentence and a one-line caveat. No sentence is filler.

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?

Because there is no output schema, the enumerated field list is what makes this tool callable with confidence, and the signing-secret exclusion prevents a wasted expectation. The only gap is the empty-state behavior — 'if any' implies but does not describe the not-configured response.

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 takes zero parameters and the description accordingly adds no parameter guidance; baseline 4 applies. The enumerated return fields are useful but belong to behavioral disclosure rather than parameter meaning.

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 retrieval: 'the webhook registered for this API key', and enumerates exactly what is returned (url, filters, active state, consecutive failures, last success, last error). The scope qualifier and the explicit field list make it trivially distinguishable from set_webhook and remove_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?

'Use it to diagnose missing deliveries' gives a concrete usage context rather than leaving the agent to infer one. It does not explicitly name set_webhook/remove_webhook as the alternatives for configuration, so there is no exclusion clause, but the read-vs-configure split is obvious from the wording.

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