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

With no annotations, the description carries the full burden of behavioral disclosure. The parenthetical '(secrets are never returned)' is genuinely useful, security-relevant context that the agent could not get from the schema. However, it says nothing about whether this is a read-only operation, whether results are paginated or ordered, or what happens with an empty result set.

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?

One sentence with the resource up front and the security caveat in a tight parenthetical. Every clause earns its place, and nothing is buried or wasted.

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 no-parameter read tool, the definition covers what it returns and what it deliberately omits (secrets). Since there is no output schema, the description could say more about the shape of an endpoint record (URL, events, status), but the essential calling information is present.

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 nothing to disambiguate, and the description does not need to explain filtering or paging inputs.

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?

Names a specific verb and resource: 'List registered webhook endpoints.' This cleanly separates it from create_merchant_webhook, list_merchant_webhook_deliveries, and replay_merchant_webhook_delivery, which deal with creation or delivery history rather than endpoint listing. It stops short of explicitly naming those siblings, so it lands at 4 rather than 5.

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 listing verb implies the use case (inspect configured endpoints), but there is no explicit when-to-use statement, no prerequisite or permission note, and no pointer to list_merchant_webhook_deliveries for delivery history. The agent must infer the boundary from the noun alone.

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