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

The description goes well beyond annotations by disclosing critical behavioral traits: the signing secret is returned exactly once and must be stored immediately, deliveries are signed and at-least-once with up to 6 retries, and the same event ID is used for deduplication. This is rich context that an agent needs to handle deliveries correctly. No contradictions with annotations.

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: purpose, return value warning, delivery signature, and retry/dedupe behavior. It is front-loaded with the core action, and the length is appropriate for the complexity of webhook registration.

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?

Despite having no output schema, the description covers the essential context: what events are available, what is returned (webhook_id and secret), and how delivery behaves (signing, retries, dedupe). This is complete for a registration tool with only 2 parameters, and the agent can proceed confidently.

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%, so the baseline is 3. The description adds value by clarifying the 'events' parameter semantics: it explains that 'compel.ready' means 'renderable - call start_render' and that omitting events or passing ['*'] subscribes to all. This goes beyond the schema's enum list and enhances the agent's understanding of parameter usage.

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 starts with a specific verb+resource: 'Register an HTTPS endpoint to receive signed push notifications'. It clearly distinguishes this from other webhook tools (delete, list, rotate, update, test) by focusing on initial registration. The event types are also enumerated, making the tool's purpose 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 implies when to use this tool (when setting up a new webhook) and provides context about event subscription and delivery. However, it does not explicitly mention alternatives or exclusions, such as using update_webhook to modify an existing webhook. Still, the context is sufficiently clear for an agent to select this tool appropriately.

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