save_attachment

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

The description adds significant behavior beyond the annotations: it discloses the 25 MB decoded size limit, the return format (path only, keeping bytes out of context), and safety guarantees (no overwrite, no directory creation). Annotations only provide readOnly/destructive hints, so this extra context is valuable and consistent.

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 three compact sentences, each earning its place: first states the core action and return value, second gives usage guidance compared to a sibling, third states important safety constraints. It is front-loaded with the primary purpose.

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 full parameter schema coverage, a clear output schema, and the description adding usage and behavioral context, the tool is well-specified. The description covers edge cases (size limit, no overwrite, no directories) and guides an agent toward the correct invocation without missing critical information.

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% with each of the 5 parameters fully described. The description does not add new per-parameter meaning beyond the schema, so the baseline 3 applies. It does clarify the overall purpose of the output_path behavior (server-side, parent dir must exist), which is already in 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 clearly states the action ('Write one attachment') and the resource (a local file on the server), and distinguishes itself from the sibling tool get_attachment by specifying it returns only the path and avoids loading bytes into the conversation.

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 tells when to use this tool: 'Use this for attachments too large to read inline with get_attachment', naming the alternative and the condition. It also preemptively clarifies behavior (never overwrites, no directories created), which helps an agent decide if this is the right tool.

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