Download media from a message

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

The description adds behavioral details beyond the annotations: it explicitly states the file is written to disk, returns a local path, and explains the rationale for not returning inline. This complements the readOnlyHint (which concerns system state) and idempotentHint by clarifying the side effect of creating a local file.

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-loading the primary action and resource, and providing a concise rationale for the design choice. There is no redundant information, making it easy to scan and understand.

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 tool with no output schema, the description fully specifies what the tool does (saves media), what it returns (local path), and why it behaves that way. It is complete for an agent to decide when to invoke it and what to expect.

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 description coverage is 100%, so the baseline is 3. The tool description does not significantly enhance parameter understanding; it only lists media types and implies that peer and message_id identify the message. The parameter descriptions in the schema already cover the meaning adequately.

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 (save media) and the resource (photo, video, document, or voice note attached to a message), and specifies the output (local path). It distinguishes the tool from siblings like send_file or forward by focusing on downloading media from a message.

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 for when to use this tool (when media needs to be saved locally) and explains why it is used instead of returning inline (base64 is enormous and unreadable). However, it does not explicitly name alternative sibling tools, so it falls short of the highest 'explicit alternatives' level.

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