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

Annotations already declare idempotentHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds real value by disclosing that omitted fields are preserved, that a new URL is re-validated, and that the secret is untouched — but it says nothing about what the response contains or whether deliveries are paused during revalidation.

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?

Four short clauses, front-loaded with the scope ('On one site of the account, named in site') then the mutation semantics. Slightly telegraphic phrasing ('Its secret stays: the person makes a new one') costs a little clarity but 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 5-parameter partial-mutation tool with no output schema and 60% schema coverage, the description covers scope, optionality and the URL re-validation side effect. It leaves open return values, permission requirements, and whether the enum'd event swapped in resets delivery state — gaps an agent must guess at.

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 60%, and the description reinforces the three mutable fields (name, event, URL) plus the 'site' scoping and the 'webhook' identifier, and its 'what is left out stays' line clarifies optionality. It adds no format or syntax detail beyond the schema, so baseline-plus 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 and resource ('Changes a webhook's name, event or URL') and scopes it to one site named in the 'site' parameter. It is clearly distinguishable from create_webhook and delete_webhook, 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?

The phrase 'what is left out stays' tells the agent this is a partial update, which is the key usage decision versus a full replace. The secret note also redirects the agent out of this tool for that operation, but there is no explicit statement of prerequisites or when not to use it.

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