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

With no annotations, the description carries the behavioral burden. It explicitly says the tool does not trigger a real event and that it returns headers, the exact body, and a ready-to-run curl command, strongly implying it does not send the request itself. This provides useful, non-obvious behavioral context, though it could be even more explicit about having no side effects.

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 short, purposeful sentences: the goal, the supported providers, and the return value. It is front-loaded with the primary purpose and contains no filler or redundant restatement of the tool name.

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 five parameters and no output schema, the description still covers the key practical facts: what it builds, why, what providers are supported, and what the caller receives. The Twilio-specific target_url caveat lives in the schema, and the return components are summarized well enough for a caller to understand the tool's output.

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 80%, so the schema already documents most parameters well. The description adds the provider list and the core purpose, but it does not add meaningful parameter-level semantics beyond what the schema provides. Baseline 3 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 states a specific verb ('Build'), a specific resource ('webhook body with a VALID signature header'), and a clear objective ('test a handler's signature verification without triggering a real event'). It also lists supported providers, which distinguishes it from sibling tools like verify_webhook_signature.

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 clearly identifies when to use this tool: when you need to test signature verification without sending a real event. It does not explicitly name alternatives or state when not to use it, but the intended use case is well implied and differentiated from generating real webhooks.

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