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

Annotations already declare non-readonly, non-idempotent, open-world behavior. The description adds useful context beyond them: a real event is delivered to the customer endpoint immediately and the HTTP status is reported, plus an auth requirement ('needs a key'). It does not describe the event payload shape or any rate/side-effect caveats on the receiving endpoint.

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?

Two short sentences, front-loaded with the action and followed by the observable result. 'Needs a key' is terse but carries a real prerequisite; nothing is redundant.

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 single-parameter tool with full annotation coverage, the description covers the action, the immediate side effect, the auth prerequisite, and the return value (HTTP status), so no output schema is needed. Only the absence of guidance toward sibling tools like webhook_deliveries keeps it below 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?

Schema coverage is 100% and the schema already explains the id format (wh_01JB2X3Y4Z) and points to list_webhooks. The description only implies 'one of your endpoints' and adds no syntax 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 and resource: sends a webhook.test event to one endpoint and reports the HTTP status. This clearly separates it from create_webhook, update_webhook, and webhook_deliveries, though it never names those siblings explicitly.

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?

'Send ... now' implies an immediate one-off test rather than a configured recurring delivery, which is implied usage guidance. There is no explicit statement of when not to use it or which sibling to use instead (e.g. webhook_deliveries for past attempts).

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