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

Annotations already declare the mutation profile (readOnlyHint=false, idempotentHint=false, destructiveHint=false, openWorldHint=true), so the bar is lower. The description adds genuinely non-obvious behavior: the response returns the signing secret, which matters for later signature verification and is not implied by any annotation or schema field. It does not mention that the endpoint may need verification or that the secret is only returned at creation time.

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 with no filler; the action and its effect come first, and the return-value fact is second. Every clause carries information an agent would not get from the schema alone.

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?

A six-parameter mutation tool with no output schema benefits from the explicit note about the signing secret in the response. However, defaults are unaddressed (what happens if events and all_events are both omitted), and there is no guidance on endpoint validation or idempotency, leaving real gaps for a creation tool with a nested filter parameter.

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?

At 67% schema coverage, the schema already documents url, events, filter, and all_events in detail. The description reinforces which event families exist but adds nothing about the events-vs-all_events interaction, the filter rule object, or the undocumented name/enabled parameters. Baseline 3 is appropriate.

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+resource ("Create a webhook") and immediately explains the effect: Emailit POSTs email, domain, contact, and campaign events to the URL. That is clearly more than a restatement of the name. It stops short of distinguishing itself from update-webhook or test-webhook, which are the nearest ambiguous siblings.

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?

No explicit guidance on when to create a new webhook versus updating an existing one, nor any pointer to test-webhook or list-webhooks for verification. The only implicit cue is the event categories listed, which hints at the subscription use case but never states prerequisites or exclusions.

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