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

The description says the tool 'upload[s] it to S3', which is a write side effect, while the annotations declare readOnlyHint=true. This is a direct annotation contradiction, making the behavioral signal unreliable for an agent.

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 compact and well-structured: a short summary block and a return contract. Every sentence earns its place, and the key action is front-loaded.

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 simple two-parameter tool, the description covers the operation, parameter source, and return shape, which is especially important because there is no output schema. It does not describe failure cases or size limits, but the core calling contract is sufficiently clear.

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?

The schema already documents both parameters fully, so the baseline is 3. The description adds value by instructing that both values come from search_emails results and that both should be provided, clarifying provenance and intended usage beyond the schema.

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 states a specific action: fetch an email attachment, upload it to S3, and return a URL. It conveys the resource and outcome well, though it does not explicitly distinguish itself from sibling tools like read_attachment or list_attachments.

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?

It gives a clear usage context: 'Use this when you need to access a file attached to an email' and points to where the identifiers come from. It does not provide explicit exclusions or alternative tool guidance, so it stops 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.