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

Annotations already mark this as a non-readonly, non-destructive, non-idempotent write, and the description adds genuinely non-obvious behavior: the signing secret is returned exactly once and cannot be re-fetched, signatures must be verified against the raw body, and deliveries may be retried. That is real value beyond the structured fields. It stops short of stating auth/permission requirements or the response shape.

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?

Three short sentences, front-loaded with the verb and resource, each carrying distinct information (what it does, one-time secret handling, retry behavior). No filler, though the retry remark sits slightly out of priority order behind the more critical secret warning.

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 one-parameter create tool with full schema coverage and no output schema, the description covers the key gotchas an agent must relay (secret shown once, raw-body verification, retries). It does not cover whether `events` must be non-empty or whether `enabled` defaults to true, minor gaps given the schema documents them.

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 single nested `data` object documents `url` and `events` inline, so the description adds nothing about parameters. The secret/raw-body sentence describes delivery behavior rather than the accepted inputs, so 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 specific verb and resource ('Create a webhook') in the first two words, which is unambiguous against siblings like create_api_key or create_tool. It does not explicitly differentiate from update_webhook or delete_webhook, but the verb carries that distinction on its own.

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?

There is no statement of when to use this versus update_webhook or list_webhooks, no prerequisites (e.g. that the receiver URL must be public HTTPS and reachable), and no exclusions. The note about the signing secret is operational advice, not usage guidance.

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