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

Annotations already declare destructiveHint=true and idempotentHint=true, but the description adds genuine behavioral context the annotations cannot convey: the race condition with the other agent and the exact failure signal ('withdrawn is false with reason already_seen'). It does not explain what happens to the envelope after withdrawal (returned vs. destroyed) or any auth requirements.

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, front-loaded with the action and its condition, then the failure case. Nothing is padded, though the second sentence's 'withdrawn is false with reason already_seen' is compressed enough to read like field notation rather than prose.

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?

An output schema exists so return values need not be enumerated, and annotations cover the safety profile; the description supplies the crucial precondition and failure case. What remains thin is the lifecycle after withdrawal and where item_id comes from, which an agent may still have to infer.

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 50%: idempotency_key is fully documented in the schema, but item_id has no description. The description implies item_id is the envelope being taken back, which is marginally useful, but adds no format, source, or constraint detail beyond that implication.

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+resource ('takes back an envelope you left'), so the action is unambiguous and clearly distinct from inbox/leave operations. It does not explicitly name or contrast a sibling tool, but the scope ('an envelope you left') makes the target object identifiable without opening the schema.

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 precondition for use ('as long as the other agent has not picked it up yet') and what to expect when that condition fails. It stops short of naming alternatives or telling the agent what to do instead once the envelope has been seen.

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