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

Annotations give the safety profile (readOnlyHint=false, destructiveHint=false, openWorldHint=true), and the description adds real context beyond them: the payload is a dummy with test:true, it is signed, it is rate-limited to once per minute per Webhook, it requires the forms:test scope, and it can only target the already-saved URL. That is exactly the kind of behavioral detail an agent needs before triggering outbound traffic.

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 first sentence is dense and front-loaded with event name, test flag, return value, scope, and rate limit — every clause earns its place. The second paragraph is longer generic safety boilerplate that is not specific to this tool, slightly diluting the payload.

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 two-parameter, non-destructive webhook test tool with no output schema, the description covers target determination, payload semantics, rate limits, auth scope, and side effects. The only gap is that 'return the result' does not sketch the response shape, which matters somewhat since no output schema exists.

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%, with both 'site' and 'id' fully documented in the schema (including that id comes from webhooks_list). The description adds only the negative clarification that no URL can be supplied, which is a marginal increment over the schema's own documentation, 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 concrete verb and resource (send a signed dummy 'webhook.test' payload to a saved form Webhook and return the result) and scopes it with the event name and test flag. It is clearly distinct from webhooks_list, webhooks_get, and webhooks_update, which manage or read webhooks rather than exercise them.

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 [When to use] block gives only generic guidance ('changes data or sends notifications... only when the user explicitly asks') plus a prompt-injection warning, and does not name alternatives such as send_test or booking_test that an agent might confuse with this one. The tool-specific constraint ('only goes to the saved URL, which cannot be given here') is useful but describes behavior more than when to choose this tool.

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