Create a webhook endpoint

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

Adds context the annotations don't carry: the response includes a one-time `secret` used to verify the `Perly-Signature` header, and live keys are refused. That is exactly the operational detail an agent needs. It still omits what happens with duplicate URLs or how event defaults apply, so it isn't exhaustive.

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?

Four short sentences, front-loaded with purpose, then the secret caveat, then the key restriction. Every sentence carries information the agent would otherwise miss.

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?

For a small mutation tool with annotations covering safety and no output schema, this is close to sufficient — it explains the critical return value and the key restriction. Only the parameter-level details (URL format, description semantics) are left entirely to the bare schema.

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 only 33% — `enabled_events` is described in the schema, while `url` and `description` have no descriptions anywhere. The tool description says nothing about URL requirements (HTTPS, reachability) or length limits, so it fails to compensate for the gap.

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 names a concrete verb and resource ('Create a webhook endpoint'), which is unambiguous on its own. It never explicitly contrasts itself with create_* siblings or with list/delete_webhook_endpoint, so it stops short of full sibling differentiation.

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?

'Test keys only: refused with a live key' is a real precondition that steers the agent, which is more than most definitions offer. There is still no guidance on when to create vs. reuse an existing endpoint, or on related tools such as verify_webhook_signature.

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