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

With no annotations provided, the description carries the full burden of disclosing behavior. It transparently reveals that the tool is idempotent ('same key return the same receipt') and guarantees no duplicate sends ('never send twice'), which are essential behavioral traits for a replay operation. It does not cover auth needs or failure modes, but the disclosed idempotency semantics are highly valuable.

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 two sentences long, front-loads the core purpose, and packs critical behavior into the second sentence without redundancy. Every clause earns its place, making it exceptionally concise 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?

For a tool with three required parameters and no output schema, the description covers the essential context: what it does, the idempotency requirement, and the guarantee against double-sending. It lacks detail on what the 'receipt' contains and what happens on failure, but these are secondary to successful invocation. Given the absence of annotations, the description is fairly complete, though a brief note on the response would push it to a 5.

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 schema provides 100% parameter coverage, so the baseline is 3. The description enhances this by explaining that the idempotency_key must be 'caller-stable' and describing the retry semantics, which adds practical meaning beyond the schema's 'Stable unique key for this replay operation.' This pushes it to a 4.

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 opens with 'Redeliver one immutable webhook event,' which pairs a specific verb (redeliver) with a specific resource (webhook event) and a critical qualifier (immutable). This clearly differentiates it from sibling tools like create_webhook, delete_webhook, and list_webhook_deliveries, leaving no ambiguity about its function.

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 indicates the tool is for redelivering a webhook event and stresses the necessity of a caller-stable idempotency key, including guidance on retry behavior ('retries with the same key return the same receipt and never send twice'). However, it does not explicitly state when to prefer this over alternatives or when not to use it, so it stops short of a 5.

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