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

No annotations are provided, so the description carries the full burden, and it delivers: automatic normalization of mismatched sizes/frame rates/audio, defined behavior for audio-less and audio-only clips, credit cost per output minute, job_id polling via get_job for long jobs, and 1-hour link expiry. This is unusually rich behavioral disclosure.

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?

Six tight sentences, front-loaded with the core operation, then behavior, then cost and lifecycle. Every sentence carries distinct information with no 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?

With no annotations and no output schema, the description supplies the operational essentials an agent needs: cost model, async job handling via get_job, and result expiry. Nothing critical to correct invocation 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% and every parameter (urls ordering, format defaults, quality, max_height) is already documented in the schema. The description adds no format, ordering, or default detail beyond what structured fields provide, so the baseline 3 applies.

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 ('Join several video or audio files end to end'), which clearly distinguishes it from siblings like trim_media, convert_media, and edit_video. An agent can identify the operation without opening the schema.

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?

Gives clear context for when this applies ('mixed sources just work', audio-only/video-only handling) and how to follow up on long jobs via get_job. However, it never names or excludes sibling alternatives (e.g. trim_media, convert_media), so routing among similar media tools is left to inference.

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