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

Annotations already establish read-only, idempotent, and non-destructive behavior. The description adds valuable behavioral context beyond the annotations by explaining the asynchronous nature of delivery callbacks and warning that 'sent' right after sending is normal. This helps set correct agent expectations without contradicting any annotation.

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?

The description is two sentences of tightly packed, relevant information. It front-loads the core purpose and status values, then adds the timing nuance without any filler or repetition of schema details.

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 single-parameter read-only lookup tool with annotations covering safety, the description covers the essential operational context: what statuses to expect and the asynchronous delay. No output schema exists, but the listed statuses imply the return content well enough. It does not discuss error cases like unknown IDs, but this is a minor gap for such a simple tool.

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 0% and the sole parameter 'id' is only typed as string. The description implicitly ties this id to an email sent via send_email, giving it some meaning, but it does not explicitly state that the id should be the value returned by send_email or how to obtain it. The compensation is minimal but not absent.

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 clearly identifies the tool as retrieving the status of an email sent via send_email and enumerates the possible values (sent, delivered, bounced, complained). It is specific about the resource and verb, though it does not explicitly differentiate itself from sibling tools beyond the send_email relationship.

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: it is meant to be used after send_email to check delivery status, and it explains that a 'sent' status immediately after the call is expected due to Amazon's callback delay. It does not explicitly name alternatives or exclusions, but the intended usage situation is clear.

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