download_video

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

With no annotations, the description carries the burden of disclosure. It transparently states the side effect (writing to local filesystem) and the return type (absolute path). It does not mention overwrite behavior or error handling, but for a simple download tool the key behaviors are disclosed.

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-loaded with the action, and contains no filler. Every word contributes to understanding the tool's purpose, output, and side effect.

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 2-parameter tool with no output schema, the description covers the purpose, the operation, the side effect, and the return value. The schema provides additional parameter details, and together they give a complete picture. No critical information 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?

Schema coverage is 100%: both message_id and output_path have detailed descriptions already in the input schema. The tool description adds only general context about the file type (MP4) and return path, not additional parameter-level semantics. Baseline 3 is appropriate when the schema does the heavy lifting.

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 ('Download'), the resource ('a saved item's video'), the output format ('as an MP4 file'), and the return value ('absolute path'). It distinguishes from siblings by focusing on video download and filesystem output, which is unique among the listed tools.

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 implies when to use the tool: when you need a saved item's video as a local MP4 file. It provides clear context but does not explicitly name alternatives or exclusions. The schema for message_id further signals that it works with items from search_bucket or list_recent, complementing the description.

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