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

Without relying on annotations, it discloses that the payload is re-signed with the key's current secret, that dedupe is possible on the stable id, that only one attempt is made with no retries, that the call is free, and that the response contains the outcome plus the updated delivery. Rate windows and exact error codes are given, and nothing contradicts the non-idempotent, non-destructive 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?

Front-loaded with the operation, then the guarantees, then limits and error codes – each clause carries information an agent needs. It is dense and semicolon-packed rather than wasteful, though slightly harder to scan than a bulleted limits section would be.

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?

There is no output schema, and the description compensates by saying what the response contains. Combined with the retry, idempotency, quota, and 404/409 semantics, an agent has everything needed to call this correctly and interpret the result.

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 100%, so both delivery_id and api_key are already documented in the schema. The description reinforces that delivery_id refers to an already-sent delivery whose id survives the redelivery, but adds no new format, sourcing, or constraint detail beyond the schema, so the baseline 3 applies.

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 verb+resource with full scope: re-send one existing delivery, same event id/body, freshly signed, to the original URL. That scope ('to the URL it was first sent to') implicitly separates it from test_webhook, which sends a new test event.

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?

Strong when-not guidance: 409 delivery_pending, 404 delivery_not_found, and three distinct 429 rate limits are spelled out, so an agent knows the preconditions and the failure paths in advance. It does not explicitly point to a sibling (e.g., test_webhook) for the send-a-test-event case, so it falls short of a full 5.

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