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

Annotations only supply `idempotentHint`, so the description carries the rest and does so well: it states this is a partial update where omitted fields are untouched, and that the signing secret is never rotated so existing verification code keeps working. Those are exactly the mutation semantics an agent needs and cannot derive from the schema or annotations.

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 and the three mutation cases are front-loaded in the first sentence, and the behavioral notes follow. The middle clause justifying the tool's existence ('the server could diagnose a problem it could not fix') is meta-commentary that does not help an agent decide or invoke, a small amount of waste.

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?

With an output schema present, return values need no explanation, and the description covers mutation scope and secret non-rotation. It omits permission/auth prerequisites and any rate or delivery-side effects, but for a 5-param partial update with full schema coverage this is close to complete.

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% and the per-parameter text is already detailed (events replaces entirely, enabled stops deliveries, URL must be public), so the baseline is 3. The description reinforces intent with real-world framing ('repoint `url` after a tunnel restarts') but adds no syntax or format detail beyond the schema.

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?

Specific verb ('Change') plus resource ('an existing webhook endpoint'), then enumerates the three concrete mutations it supports: flipping `enabled`, repointing `url`, and replacing subscribed events. This clearly separates it from `volanea_create_webhook_endpoint` and `volanea_test_webhook_delivery`.

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 triggering scenarios (endpoint stuck at `enabled: false`, tunnel restart changing the URL) and cross-references `volanea_get_project_status` as the diagnostic that surfaces the problem. It stops short of naming explicit alternatives or when-not-to-use conditions, but the usage context is unambiguous.

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