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

Annotations already declare destructiveHint=true and readOnlyHint=false, so the description does valuable work clarifying that the result is a NEW file and that inputs are joined rather than mutated. It also discloses the return payload ('output path + duration'), which the annotations cannot convey. It omits the overwrite-refusal behavior, but that is covered in the schema.

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: the core operation and output first, then the resolution constraint, then the return value. Nothing is wasted and nothing important is buried.

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 output schema, the description correctly tells the agent what comes back (output path + duration), and it flags the resolution homogeneity requirement that would otherwise cause silent failures. Only edge-case behavior (failure handling, large input limits) is unaddressed, which is minor for a simple concatenation 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 description coverage is 100%, so the schema already explains ordering, output default naming, the ignored 'confirm' flag, and overwrite refusal. The description only echoes ordering ('in order') and adds no syntax or format detail beyond the schema, making the baseline 3 appropriate.

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+resource ('Stitches multiple videos end-to-end, in order') and the output artifact ('one NEW file'), with a concrete example ('assemble separate acts'). An agent can distinguish this from video_trim, video_reframe, and video_export_gif purely from the description.

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?

Provides a clear use case ('assemble separate acts') and a prerequisite constraint ('All inputs should share a resolution for a clean result'), which is actionable guidance. It stops short of naming alternative sibling tools or stating when not to use it, so it falls just below the top tier.

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