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

Annotations already indicate readOnlyHint=false and destructiveHint=false, so the agent knows this is a non-destructive write operation. The description adds valuable behavioral constraints not in the schema: the 25MB size limit and the list of supported file types. This goes beyond what annotations provide.

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 two sentences with no redundancy. It front-loads the core purpose, then packs constraints and the alternative tool reference into the second sentence. Every sentence 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?

For a simple file-attachment tool with rich annotations and a fully-described schema, the description covers purpose, size/type constraints, and sibling routing. It omits return-value details, but since there is no output schema and the action is straightforward, the description is sufficiently complete for correct invocation.

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% and the schema describes each parameter, so the baseline is 3. The description adds semantic value by explicitly listing supported MIME types (which the schema only references as 'one of the supported types') and adding the critical 25MB size constraint relevant to contentBase64. This enriches parameter understanding 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 states exactly what the tool does: 'Attach a document or image to a standalone task.' It uses a specific verb and resource, and explicitly distinguishes itself from create_standalone_comment by saying that tool is for plain text notes. An agent can clearly tell this from siblings.

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 explicit guidance: 'Use create_standalone_comment instead for plain text notes — this tool is for actual files.' This tells the agent when to choose an alternative and when to use this tool, leaving nothing to inference.

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