Download ServiceNow attachment

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

Annotations already declare readOnlyHint and openWorldHint, but the description adds valuable behavioral detail: the output is base64 and large files will be refused referencing SN_MAX_RESULT_CHARS. This goes beyond what annotations provide and sets clear expectations for the 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 extremely concise, using two short sentences. The primary action and output format are front-loaded, and the key limitation is stated without ambiguity. Every word contributes to understanding.

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 download operation with only one required parameter and no output schema, the description covers all essential aspects: what it does, the return format, and a critical size limitation. No additional context is needed for an agent to invoke it correctly.

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 input schema provides complete descriptions for both parameters (instance and attachment_sys_id), so the description does not need to add param-level detail. It does indirectly reference a size constraint via SN_MAX_RESULT_CHARS, but this is not tied to a specific parameter. This aligns with the baseline for high schema coverage.

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 ('Download') on a specific resource ('an attachment's bytes') and specifies the return format ('base64'). This distinguishes it from sibling tools like credential management or instance listing, making its purpose unambiguous.

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 provides clear context for when the tool is appropriate (downloading attachments) and includes a critical limitation ('Large files are refused') that guides usage. It does not explicitly name alternatives, but no direct alternative exists among the listed siblings, so this is sufficient.

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