download_attachment

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It clearly states that image bytes are never returned inline, explains the rationale (truncation hazard), and describes the verification output (byte length and sha256). This goes well beyond the schema and gives the agent a solid understanding of the tool's behavior and limitations.

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 compact (three sentences) and front-loads the core action. Every sentence serves a purpose: the first states the two modes, the second explains return values, and the third provides an important behavioral caveat. No wasted words.

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?

Given the tool's moderate complexity (two modes, no output schema, no annotations), the description is exceptionally complete. It covers what the tool does, how to use it, what it returns, and a key limitation. The schema handles parameter details, so the description focuses on the conceptual and behavioral context, making it fully adequate 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?

The schema already provides 100% coverage of the three parameters, so the baseline is 3. However, the description adds meaningful context: it clarifies the trade-off between destPath and signedUrl and reinforces that inline bytes are not returned, which helps the agent choose the right parameter combination. This extra semantics justifies a 4.

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 purpose with a specific verb and resource: 'Download a stored attachment'. It also distinguishes between the two modes (writing to a file path or generating a signed URL) and differentiates the tool from siblings like create_attachment and delete_attachment by focusing on retrieval.

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 explicitly explains when to use each parameter (destPath vs. signedUrl) and implicitly warns against trying to get inline bytes, referencing the 'truncation hazard create_attachment exists to avoid'. This provides clear context and even names an alternative tool and why it's not suitable for downloading.

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