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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered. The description adds real value beyond that by disclosing the null-return behavior and the closed set of outcome values, which are not in any structured field since there is no 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?

Two short sentences, front-loaded with the resource and outcome set, then the edge-case behavior. No redundant restatement of the title or annotations, and every clause carries information.

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 must carry return-value semantics, and it does so by listing the outcome states and the null case. It stops short of saying whether the result includes supplementary detail such as bounce reason or timestamp, which leaves a small gap for an agent reasoning about the response.

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?

There is one parameter (messageId) with 0% schema description coverage; only the uuid format is machine-readable. The description implies the ID identifies an outbound message, but never clarifies whether it is the message ID versus a campaign-contact or queue ID, nor what happens with an unknown ID. Baseline 3 given the schema still conveys type and format.

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 (returns the saved result of an outbound message) and enumerates the possible outcomes: sent, bounced, stopped, rejected or unconfirmed. The phrase 'after it leaves the queue' implicitly separates it from getQueuedMessage and the queued-message family, though it never names a 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?

The description establishes a clear usage condition ('after it leaves the queue') and tells the agent what to expect when that condition is not met ('Returns null when there is no result yet'). It does not explicitly name checkMessageDelivery or getQueuedMessage as alternatives, so the routing decision still requires inference.

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