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

Annotations already declare readOnlyHint=false and destructiveHint=false, so the safety profile is covered. The description adds the useful return detail of webhook and A2A URLs, which is genuine context. It remains silent on idempotency (relevant given the idem.* siblings), whether repeated calls create duplicate inboxes, and any auth or quota constraints.

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, with the action front-loaded and the return value second. There is no padding, though the description is arguably too thin for a provisioning call rather than too long.

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's mention of returned webhook and A2A URLs is essential and correctly included. However, for a creation tool whose siblings include idempotency primitives, the description omits whether the operation is idempotent or repeatable, leaving an agent unsure about retry safety.

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 there is nothing to document and the baseline is 4. The JSON schema is an empty object and the description correctly does not invent parameter behavior.

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 and resource ('Create an inbox'), which is distinguishable from the sibling read-side tools inbox.ack, inbox.poll, and inbox.wait. It does not mention how it relates to the other create-style siblings (keys.create, idem.begin), so differentiation is implicit rather than explicit.

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?

There is no guidance on when to call this versus other setup tools such as keys.create or the idempotency pair idem.begin/idem.commit. An agent must infer from the name alone that this is the provisioning step before polling.

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