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

Annotations only declare safety flags (non-read-only, non-destructive, not idempotent). The description adds genuinely useful behavior beyond that: cost ('Consumes one inbox credit') and the critical fact that 'Callback arrival does not restart a stopped assistant,' which an agent might otherwise assume incorrectly. Return format is handled by the output schema.

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?

Four short, dense sentences with the capability front-loaded and lifecycle caveats after. No filler, though the credit-cost sentence and restart caveat could be merged slightly more tightly.

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 3-param, all-optional creation tool with an output schema and annotation safety profile, the description covers purpose, lifecycle caveat, and cost. Nothing essential for correct invocation appears missing.

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 coverage is 100% with all three optional params (label, idempotency_key, expires_in_seconds) fully documented in the schema, including the 409-on-reuse semantics and lifetime bounds. The description adds no parameter detail, so the baseline 3 applies.

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 capability: 'Provision a reachable intake URL, then retrieve events in a later run,' which clearly identifies this as the creation/provisioning tool among inbox siblings. It doesn't explicitly name a sibling like get_inbox or delete_inbox, but the create-vs-read/delete distinction is inferable from the provisioning framing.

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?

It gives clear context for when this tool is appropriate: 'after the agent process exits' and for callbacks that must survive a stopped assistant. There is no explicit when-not or routing to an alternative sibling, so it falls short of a 5.

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