get_attachment

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

With no annotations provided, the description carries the transparency burden. It discloses a key behavior: 'Returns images directly so Claude can view and analyze them,' which indicates the response format is the file content itself, not a URL or metadata. This adds value beyond what the input schema specifies, though it doesn't detail error handling or non-image file behavior.

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, front-loaded with the primary action and followed by a helpful clarification. No unnecessary words, 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 tool with one parameter and no output schema, the description covers the core purpose, return behavior, and required input source. It doesn't mention error cases or file type limitations, but the simplicity of the tool makes this acceptable. Overall, it provides enough context 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?

Schema coverage is 100%, and the schema already fully documents the only parameter, message_id, including its origin ('from conversation results'). The description repeats this guidance but adds no new meaning, so the baseline of 3 is appropriate.

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 the tool's function: 'Get an attachment (image, file) from a message.' It also adds purpose nuance by explaining that images are returned directly for viewing and analysis, which distinguishes it from sibling tools that read messages or retrieve conversation metadata.

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 by specifying the prerequisite: 'Use message IDs from get_conversation results.' This tells the agent exactly where to obtain the required parameter. It doesn't explicitly discuss alternatives or exclusions, but the purpose is distinct enough among siblings that this guidance is sufficient.

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