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

Annotations already declare readOnly/idempotent/non-destructive, yet the description adds substantial context beyond them: the exact signature scheme (Pixeloa-Signature with HMAC-SHA256 construction), retry backoff up to 12h, auto-disable after 20 consecutive failures, and the read_usage scope requirement. This is genuinely useful operational context an agent wouldn't get from the structured fields.

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?

Front-loaded with the core purpose, then supporting detail. The HMAC signature breakdown is somewhat tangential to invoking a list call and lengthens the definition, but it is dense and each sentence carries information rather than filler.

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?

No output schema exists, so ideally the description would sketch the returned shape (endpoint fields), and it only says 'endpoints and the event types.' Still, for a zero-parameter, read-only list tool with annotations covering the safety profile, this is largely complete; only the return structure is left implicit.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate; the 4 baseline applies. The description correctly implies a no-argument call scoped to the account.

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 precise verb+resource: 'List the account's webhook endpoints and the event types.' No sibling tool covers webhooks (siblings are item/catalog/agent tools), so the agent can route here without ambiguity. It also clarifies the human-created nature of endpoints, sharpening what the resource is.

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 clear usage context: endpoints are created in the dashboard, and a key 'can list them but never add or redirect one,' which bounds what this call can do. It also states the required scope (read_usage). It stops short of naming an alternative tool or a when-not-to-call condition, but none is needed given there are no sibling webhook tools.

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