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

Annotations already declare readOnlyHint=false, openWorldHint=true, idempotentHint=false, and destructiveHint=false, so the agent knows this is a non-destructive but non-idempotent write with external effects. The description adds that the event is 'signed' and 'one' event (reinforcing the non-idempotent single-delivery nature) and that the subscription must be active, which is useful context beyond the 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?

A single efficient sentence with the action and target front-loaded. No wasted words, though the brevity comes partly at the cost of the missing parameter and behavioral detail.

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?

With only two parameters, no output schema, and 0% schema coverage, the description is too thin for the task. It never explains the subscriptionKey parameter or what a successful test delivery returns or affects, leaving the agent to infer invocation details.

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 0%, so neither subscriptionKey nor eventType is documented in the schema, and the description adds no meaning about either. The eventType enum is self-documenting, but subscriptionKey's role (which subscription to target, key format) is left entirely unexplained, so the description fails to compensate for the coverage 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?

States a specific verb (Send) and resource (one signed test event to an active webhook subscription), which is distinguishable from siblings like evidence_replay_webhook_delivery or evidence_webhook_health. It is clear, though it doesn't explicitly differentiate itself from those alternatives by name.

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 phrase 'to an active webhook subscription' implies the precondition that a subscription must exist and be active, and the word 'test' implies a trial/diagnostic context. However, there is no explicit when-to-use or when-not-to-use guidance versus replay or health-check siblings.

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