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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds substantial behavioral detail beyond them: the 2097152-byte inline limit, image-format sniffing, and the full set of fallback reasons (expired, erased, gated, not an image, too large) including that a signed URL is returned instead.

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, front-loaded with the action and scope, then arguments, then return-value contract. No filler and every clause carries operational 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 still specifies both branches of the return value (inline image vs. explanatory text with a signed URL). Combined with the annotation-covered safety profile and the fully described third parameter, nothing an agent needs to call this 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 description coverage is 0%, so the description carries the burden, and it defines artifactIndex precisely (0-based, from get_report's attachment list, default 0). projectId and eventId are only covered by reference to get_report, which is adequate but slightly thin for two required parameters.

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 ('Fetch one report attachment's bytes as an inline image') and ties itself to the sibling get_report by explaining that artifactIndex comes from that tool's attachment list. An agent can distinguish it from get_report and get_ticket_attachment without opening a schema.

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?

Explains that projectId/eventId are the same as get_report and that artifactIndex is the 0-based index from get_report's trailing attachment list, which implies the correct call ordering. It stops short of explicitly naming when to prefer get_ticket_attachment or when to skip fetching entirely.

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