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

Beyond the annotations (readOnlyHint=false, idempotentHint=false, openWorldHint=true), the description discloses the full behavioral profile: one attempt, no retries, 5 s timeout, signed with Roster-Signature and Roster-Event: ping, free, not counted as a job, excluded from the delivery list, and the two distinct 429 error codes with Retry-After. This is far richer than the annotations alone.

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?

Purpose is front-loaded and the dense detail is all relevant error/limit information. A few phrases ('without hiring anyone') add no value, and the single-wall-of-text format makes the fallback chain and error codes harder to scan than necessary, but nothing is truly wasted.

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 2-parameter tool with no output schema, the description covers everything an agent needs: target resolution, signature semantics, timeout/retry behavior, rate limits, distinct error codes, and side-effect profile (not a job, not in delivery list). Nothing material 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 coverage is 100%, so the baseline is 3. The description adds real meaning beyond the schema: it states the multipart fallback resolution order (explicit webhook_url → key's job webhook URL → usage-alert webhook) and that the response's target field tells you which was used. That resolves the main ambiguity an agent would have about the optional parameter.

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?

The description opens with a specific verb and resource ('Send one signed ping event to check your webhook endpoint and signature verification') and closes by naming the exact REST equivalent (POST /api/v1/webhooks/test). This clearly separates it from siblings like redeliver_webhook, list_webhook_deliveries, and set_webhook_events.

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?

It explains exactly when to use it (verify endpoint reachability and signature verification before or alongside real traffic) and names the fallback chain when no URL is supplied. It also enumerates the when-not cases explicitly: 409 no_webhook_url, 409 webhook_secret_missing, and 429 rate/daily limits.

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