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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true, so the safety profile is covered. The description adds that only active subscriptions are returned and gives the REST path, but it does not explain the implicit account scoping (the path takes accountId yet the schema has no parameters) or whether pagination applies.

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 short fragments, front-loaded with the resource, with no filler. The trailing endpoint path is marginally redundant for an agent but is compact and does convey the resource hierarchy.

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 carries the burden of describing the return value, yet says nothing about what a webhook record contains (target URL, subscribed event types) or how many come back. For a simple zero-argument list tool that is an acceptable but incomplete definition.

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?

Zero parameters, which is the baseline-4 case; nothing needs disambiguating in the schema. The description's reference to an accountId path segment is a small extra hint that account context is supplied implicitly rather than by argument.

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 the resource precisely ('Active webhook subscriptions') and clarifies it with 'message event notifications', so an agent knows this lists notification endpoints rather than something else. The verb is only implied by the tool name, and there are no semantically similar siblings to differentiate against, so a 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?

Usage is only implied: an agent can infer it should call this to discover configured webhooks. There is no statement of when to prefer it, no prerequisites, and no note about what to do when the list is empty or which sibling to use next (e.g., message or conversation tools).

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