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

Goes well beyond the annotations (readOnlyHint=false, idempotentHint=true, openWorldHint=true) by spelling out what success does and does not prove ('never proves agent processing'), what side effects are avoided ('No mail, charge, email or facility work'), and the required scope (webhook.manage). This is exactly the extra context annotations cannot convey.

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?

Dense and front-loaded: the core action and outcome come first, then caveats, prerequisites, and a docs link. It is longer than average but nearly every clause carries distinct meaning; minor tightening is possible.

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 mutating, open-world test tool with an output schema, the description covers side effects, authorization, idempotency retry guidance, and the meaning of the verdict. Return-value detail is properly left to the output schema. Only the explicit sibling contrast is missing.

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 100%, so the schema already documents all three parameters, including the staleness semantics of expected_revision. The description's note about reusing idempotency_key adds a small amount of operational context but largely restates what the schema covers, so the baseline of 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 action ('Run the Sample test') with a precise account of what happens: scanning the member's sample letter, delivering inbound.pages_ready / inbound.keywords_matched events, and returning a verdict. This clearly distinguishes it from the sibling 'test_webhook_endpoint' by framing the fictional/free sample flow.

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?

Gives concrete context: it will open/scan the sample letter 'if needed', requires webhook.manage, and shares the authorization model of /api/v1/webhooks/endpoints. It also tells the caller to reuse the idempotency_key after an uncertain mutation. It stops short of explicitly contrasting when to prefer this over test_webhook_endpoint.

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