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

With no annotations, the description carries the full burden. It discloses that bytes travel as text, that there is a size ceiling, that the encoding costs roughly a third more, and that reading requires only issue-view permission. It doesn't specify the exact size limit or error behavior, but the core behavioral traits are covered.

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 sentences, each earning its place: what it does, cost/size trade-off, and permission. The key operation is front-loaded, and there is no redundant repetition of schema content.

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 read tool with no output schema, the description covers the return format (base64), the source of the filename, the alternative for large files, and the required permission. Nothing an agent needs to call it 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 coverage is 100%, so the baseline is 3. The description adds value by saying the filename must be exactly as listed by get_issue, which clarifies an important parameter relationship beyond the schema's generic 'File name' description.

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 states a specific verb ('Read') and resource ('one file attached to an issue'), and specifies the exact output (bytes, base64-encoded). It clearly differentiates from sibling tools like add_attachment, delete_attachment, and get_issue.

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 clear context: call by issue key and filename, only needs issue-view permission, and mentions the pm-files MCP server as an alternative when saving to a path is preferable. It doesn't explicitly state when not to use this tool beyond size considerations, but the alternative is named.

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