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

Annotations already declare readOnlyHint=true, so the safety profile is covered; the description adds the non-obvious constraint 'File bytes are not returned,' which prevents the agent from expecting binary content. It does not state ordering, pagination, or behavior when a transaction has zero attachments, so it stops short of full disclosure.

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?

Three short sentences with no filler: what it lists, what it returns, what it does not return, and the related tools. Front-loaded with the resource and the field list, and every clause earns its place.

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 helpfully enumerates the returned fields and explicitly excludes file bytes, which is exactly the information an agent needs for this simple one-parameter list tool. Only the ordering and empty-result behavior are left unspecified, a minor gap given the tool's simplicity.

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 a single required parameter and schema description coverage is 100%, so the schema already explains transactionId. The description adds no format, validation, or scoping detail beyond the schema, which matches the baseline for high-coverage schemas.

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 and resource ('List the files attached to a transaction'), clarifies scope with parenthetical examples ('receipts, invoices'), and enumerates the returned fields (id, filename, mimeType, size, upload time). It is unmistakably distinct from sibling tools like create_attachment_upload_url and delete_attachment, which it names directly.

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?

Explicitly routes to alternatives: 'Use the id with delete_attachment' and 'create_attachment_upload_url adds files.' This tells the agent what to do with the output and which sibling handles the write path. It stops short of an explicit when-not-to-use clause, but the workflow chaining is clear.

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