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

With no annotations, the description carries the full burden; it does disclose the key behavioral trait that the original soundtrack is destroyed/replaced, plus file-count and 500 MB limits and credit cost per run. It omits processing time, supported audio/video formats, and how the input files are actually supplied.

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?

Only the first sentence describes the tool; the remainder is workspace/pricing boilerplate ('Welcome credits', 'Day Pass', 'See mioffice.ai/pricing') that belongs in mioffice_pricing_info. Front-loaded correctly, but the majority of the text does not earn 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?

For a tool with an empty schema and no output schema, the description does supply the essential contract: inputs (1 video + 1 audio, 500 MB cap) and output (MP4). However, how to attach files and any format restrictions are left unexplained, which is a real gap when the schema offers no parameters at all.

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 input schema declares zero properties, so there is nothing structured to rely on; the description compensates by telling the agent the invocation shape (one video + one audio file, up to 500 MB each). Baseline for 0 params is 4, and this text partially fills the gap, though it never explains the mechanism for passing those files.

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 and resource ('Add Audio to Video') and clarifies the exact effect: the supplied audio replaces the original soundtrack and the output is MP4. That distinguishes it from siblings like mio_video_mute or mio_video_normalize_audio, though it never names an alternative explicitly.

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 explains what happens when invoked but gives no guidance on when to choose this over related tools (e.g. merge, voiceover, or normalize_audio), and no exclusions. The only conditional content is pricing/workspace eligibility, not task routing.

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