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

Annotations already establish readOnly, idempotent and non-destructive behavior, so the bar is lower. The description still adds real context beyond them: the policy is human-editable only (Account > Sending rules) and must not be bypassed through another inbox, which warns the agent off a tempting workaround.

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 sentences, nothing wasted: the action and timing come first, the constraint second. No restatement of the name 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?

A read-only, closed-world getter with a full output schema, so return values need no prose. Annotations cover the safety profile and the description covers the workflow and policy-editability constraint — nothing an agent needs to call it correctly is 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?

Only one parameter with 0% schema description coverage, but the UUID format and pattern are fully specified structurally. The phrase 'this inbox's' ties the parameter to an inbox, yet the description adds no format, sourcing, or lookup guidance beyond that, so it only marginally compensates.

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 concrete verb and resource ('inspect this inbox's recipient restrictions'), scoped clearly to a single inbox and framed against the send workflow. It separates itself from get_receiving_policy by naming 'recipient restrictions' rather than receiving rules, though it never names that sibling explicitly.

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?

Gives a clear trigger ('before preparing a send') and a caution against working around the policy via another inbox. It stops short of explicitly naming alternatives or stating when-not-to-use, but the surrounding context is unambiguous.

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