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

With no annotations, the description carries the full burden and does disclose the most important non-obvious trait: the signing secret is returned exactly once and must be persisted, which directly changes how an agent should handle the response. It omits other relevant traits such as auth/permission requirements, what happens on re-registering the same URL, or whether events are delivered retried.

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 tight sentences with zero filler: the operation is front-loaded and the critical secret-handling warning follows immediately. Nothing is repeated from the schema or title.

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 two-parameter registration tool with no output schema and no annotations, the definition covers the key operational hazard (one-time secret) and the endpoint/event scope. The remaining gap — auth requirements and idempotency on repeated registration — is modest but real.

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 both the url and events parameters (including the 'omit for all events' default) are already fully documented in the schema. The description adds no parameter-level detail beyond that, which is the expected baseline when the schema does the work.

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 description states a specific verb and resource ('Register an HTTPS endpoint') plus the event domain ('signed listing events'), which is enough for an agent to identify the operation. It does not explicitly contrast with list_webhooks or delete_webhook, so sibling differentiation is only implicit.

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 'register ... for signed listing events' — an agent can infer this is for subscribing to event delivery — but there is no explicit when-to-use, when-not-to-use, or pointer to alternatives such as list_webhooks for checking existing registrations.

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