save_attachment

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

The description states 'MCP server writes the file directly', clearly indicating a write operation, but annotations declare readOnlyHint=true. This is a direct contradiction and severely misleads the agent about the tool's safety profile.

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?

Two concise sentences, front-loaded with the primary action. Every sentence contributes meaningful information (operation, platform note, path handling) with no redundancy or filler.

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?

The tool is simple with few parameters and no output schema, so the description need not explain return values. However, the contradiction with readOnlyHint leaves the agent without reliable safety information. Additionally, important details like overwrite behavior, error handling, and return values are omitted, reducing completeness for a write operation.

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 already covers both parameters with descriptions (100% coverage). The description adds extra value by explaining path behavior when a directory is provided ('original filename is used'), which goes beyond the schema's description. This additional semantic clarification justifies a score above the baseline of 3.

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?

Clearly states the action ('Save an attachment to a local file'), the resource (attachment), and the destination. It is distinct from sibling tools like get_attachment which retrieves content, making the 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?

Provides context that the server writes the file directly and works on any platform, implying cross-platform reliability. However, it does not explicitly mention when to prefer this over get_attachment or other alternatives, nor does it list exclusions.

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