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

Annotations already declare the write, non-idempotent, open-world, non-destructive profile, so the description's real contribution is behavioral: it discloses the return payload (ingest URL) and the critical fact that the read token is shown only once. That single-use warning is exactly the kind of non-recoverable consequence an agent needs. It omits inbox lifetime/expiry and whether repeated calls spawn duplicate inboxes.

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 sentences, action first and return values second, with zero filler. Every clause carries information an agent needs before calling.

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-param, no-output-schema tool this is nearly sufficient: the description compensates for the missing output schema by naming the returned ingest URL and read token. The one meaningful gap is the absence of any statement about inbox persistence or expiry, which affects how the agent should treat the token.

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?

There are zero parameters, which sets the baseline at 4, but with no parameters there is nothing for the description to clarify, so it neither adds nor loses meaning here. The brief mention of outputs is not a parameter concern and is covered under behavioral transparency.

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 leads with a specific verb and resource ('Create a webhook inbox'), making the operation unambiguous and easily separable from siblings like delete_inbox, list_events, and wait_for_event. It stops short of explicitly naming those alternatives, but the create-vs-read distinction is self-evident.

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 must call this before wait_for_event or get_event is useful, but the description never states when to create an inbox or whether one already exists. No exclusions, prerequisites, or alternatives are named.

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