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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint=false and destructiveHint=false, so the safety profile is covered. The description adds two things not in structured data: the entitlement requirement (Pro or Builder plan) and the fact that delivery statistics are returned alongside endpoints — exactly the kind of auth/entitlement context the rubric credits.

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?

Two sentences, both front-loaded with the essential information: what is returned first, the hard prerequisite second. Nothing is redundant or padding.

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 zero-parameter, annotation-rich, read-only listing tool this is nearly complete. The only gap is that there is no output schema, so the shape of "delivery stats" is left vague — an agent knows it gets stats but not which fields.

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 the baseline is 4. There is no parameter meaning the description could add, and it correctly does not invent any.

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+resource ("List all your webhook endpoints") and adds the payload content ("their delivery stats"). It is clearly distinguishable from create_webhook, update_webhook, delete_webhook and test_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?

Usage is only implied by the verb "list"; there is no explicit when-to-use or when-not-to-use statement, and no routing to siblings like get_webhook-style inspection versus test_webhook. The "Requires Pro or Builder" clause is a useful prerequisite but is a gating condition rather than usage guidance.

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