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

Annotations only declare the safety profile (not read-only, not destructive, open-world), while the description adds genuinely new behavior: a hard cap of 5 webhooks per account, HMAC-SHA256 payload signing, and the fact that a secret is returned and must be stored to verify signatures. It stops short of describing failure behavior when the cap is hit or auth requirements, so it is strong but not exhaustive.

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?

Five short sentences, each load-bearing: purpose first, then event semantics, then the quota cap, signing method, and the secret-handling instruction. No filler and no repetition of schema content.

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 no output schema, the description correctly compensates by telling the agent the response contains a secret that must be saved. Combined with the quota cap, signing details, and full parameter coverage, the only gap is error/permission behavior when the 5-webhook limit is reached.

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%, so the 3 baseline applies, but the description enriches the events enum with operational meaning (quota.warning = 80% used, quota.exceeded = 100% used, screenshot.completed = batch job done), which the bare enum values do not convey. The url parameter gains nothing beyond the schema's HTTPS requirement.

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 first sentence states a specific verb and resource ('Create a webhook subscription for event notifications'), which cleanly separates it from delete_webhook, list_webhooks and test_webhook without needing to name them. An agent can pick this tool from the sibling list on the verb alone.

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?

Usage is implied by the event catalog and the 'Max 5 webhooks per account' constraint, so an agent can infer when subscriptions make sense. However, there is no explicit when-to-use versus test_webhook or list_webhooks, and no stated precondition (e.g. verifying the endpoint first).

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