concat_media

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

With no annotations, the description carries the burden, and it does disclose the key behavioral trait: stream copy versus re-encoding and the quality/codec consequences. However, it omits what happens to an existing output file, whether re-encode is slower, and how codec mismatches in lossless mode are reported.

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 tight sentences, action first, mechanism second, with zero redundant phrasing. Nothing could be removed without losing information.

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 three-parameter tool with a fully documented schema and no output schema, the description covers the essential behavior and the mode trade-off. Remaining gaps (overwrite semantics, return value) are modest given the rich schema.

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% and the enum for mode is fully documented in the schema, so the baseline is 3. The description's 'in order' and 're-encodes when formats differ' echo but do not extend the schema's parameter documentation.

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?

States a specific verb (join) and resource (multiple video/audio files) plus the result (single file), which distinguishes it from siblings like media_convert or trim_media that transform rather than combine. It stops short of naming an alternative explicitly, but the operation is 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?

The second sentence implies when each internal strategy applies (matching files vs differing formats), which is useful, but it never says when to choose concat_media over media_convert, create_split_screen, or repeated trim operations. Usage is inferable rather than stated.

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