download_file

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

With no annotations provided, the description carries the full burden and succeeds. It discloses the default download location, subdirectory behavior, rejection of unsafe relative/absolute paths, filename sanitization, and de-duplication against existing files. This makes side effects predictable.

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 tight sentences with the core purpose front-loaded in the first sentence. The following sentences add only necessary behavioral detail about destination handling and filename behavior. There is no filler or repetition.

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 file-download tool with an output schema and no annotations, this description covers all essential operational context: target location, path-safety rules, and collision handling. Nothing critical needed to invoke it successfully is missing.

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 has 0% parameter descriptions, so the description must compensate. It does so strongly for dest_dir by explaining subdirectory selection and path-validation rules. However, chat and message_id are only implicitly tied to 'one message' and lack explicit formats or examples, leaving a modest gap.

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 states the specific operation: 'Download the file attached to one message to local disk and return its path.' It identifies the resource (a file attachment) and the result (a local path), clearly distinguishing it from sibling tools like search_files and get_messages that retrieve metadata rather than save files.

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 gives clear usage context: use it when you have a specific chat and message_id and want the attached file saved locally. It explains dest_dir semantics and path restrictions, but does not explicitly name alternatives or state when not to use this tool, so it falls short of a full 5.

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