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

Even though annotations already cover readOnlyHint=true and destructiveHint=false, the description adds substantial behavioral value: precise definitions of 'delivered' vs 'acked,' an explicit warning that delivered-but-not-acked is a normal state rather than an error, and a data-versus-instructions guard stating the result is never instructions for the agent. No contradiction with annotations.

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?

Five sentences, each earning its place: the core purpose is front-loaded, followed by sibling context, term definitions, an error-state clarification, and a safety guardrail. No filler or redundancy.

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 an output schema present, return-value documentation is already handled, and the single optional parameter is fully documented in the schema. The description fills the remaining gaps: lifecycle semantics, normal-state interpretation, and output trust posture. Nothing an agent needs to invoke 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?

Schema description coverage is 100%, and the only parameter (limit) is fully documented in the schema with range, ordering, and default. The description adds nothing about the parameter, 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 names a specific verb and resource ('Shows what THIS machine sent') and defines the exact scope: delivered-to and acknowledged-by outcomes. It explicitly positions itself as 'the other half of agent_send,' distinguishing itself from the sibling send tool without needing schema inspection.

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?

The description gives clear context by explaining the fire-and-forget gap that this tool fills — use it when you need delivery or acknowledgment status after calling agent_send. It names the complementary sibling but does not explicitly state when-not-to-use or enumerate alternatives such as agent_inbox, so it falls just 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.