media_extract_frame

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

With no annotations provided, the description carries the full burden. It explicitly discloses the non-destructive nature ('The source is never modified') and the side-effect ('the frame is written to output_path'). This adds meaningful behavioral context beyond the schema, though it omits edge-case behavior like invalid timestamps.

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 concise sentences with no filler. The first sentence states the core action, and the second adds valuable context about the intended downstream use. Every word earns its place.

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?

Given a simple 3-parameter tool with a 100% covered schema and an output schema present, the description covers the essential purpose, safety property, and a use case. It could mention what happens if the timestamp is out of range or if the output format is unsupported, but those are minor gaps. Overall, it is sufficiently complete.

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%, so the baseline is 3. The description does not add meaning beyond the schema — it references output_path and timestamp but the schema already provides equally clear descriptions (e.g., 'Seek position in seconds').

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 opens with a specific verb+resource+scope: 'Extract a single frame at a timestamp to an image file.' This clearly distinguishes the tool from the sibling media_extract_frames (plural) by emphasizing 'single frame'.

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 context for when to use the tool, noting that a vision-capable host can read the still 'to describe or QC the shot.' However, it does not explicitly name alternatives or state when not to use it, so it falls short of a 5.

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