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

Annotations only include readOnlyHint: false, which signals mutation but nothing else. The description adds valuable behavioral context: it says the tool 'renders the combined video with ffmpeg', returns a downloadable URL 'right away', and saves the result to list_my_videos. This goes beyond the annotation and sets expectations for side effects and output. However, it does not mention any potential source-video constraints (e.g., codecs, resolution) or rate limits, so a small gap remains.

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 compact (3 sentences) and front-loads the core purpose. Each sentence adds distinct value: purpose/ordering, parameter hints, behavior/return, and usage guidance. No fluff or repetition of schema facts beyond what's necessary for emphasis (ordering). It is appropriately sized and perfectly structured.

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 this is a mutation tool with 5 parameters and no output schema, the description covers all essential context: what it does, how to supply inputs (ordered list from list_my_videos), optional parameters, the return value (downloadable URL), and the side effect (saved to list_my_videos). It leaves no major ambiguity for an agent deciding to use or invoke the tool.

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 baseline is 3. The description adds crucial meaning for clip_asset_ids by emphasizing the ORDERED nature and that the first id plays first, plus the hint to get IDs from list_my_videos. It also highlights that orientation, fps, and quality are optional, but doesn't detail all parameters (e.g., project_name) — though the schema already covers those. The added ordering semantics elevate it above baseline.

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 tool stitches multiple videos into one, with a specific verb ('stitch'), resource ('several of your Switch videos'), and outcome ('ONE video, played back-to-back in the order you give'). It also differentiates from siblings by explicitly targeting combine/join/merge/concatenate use cases, which is absent in sibling names like generate_video or analyze_video.

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 explicit when-to-use guidance: 'Use this whenever the user wants to combine, join, merge, or concatenate multiple clips into one.' It also references a sibling (list_my_videos) as the source for IDs, giving practical context. No exclusions are needed; the 'whenever' phrasing is unambiguous.

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