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

Goes beyond the annotations by disclosing that provided files MERGE over the existing set and that every clip playing the composition re-renders — an important side effect. It does not explain what specifically is destructive or what permissions are needed, but the annotations already signal destructive and idempotent behavior.

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?

Four dense sentences, front-loaded with the core action, then merge semantics, side effects, and preview behavior. No wasted clauses.

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?

Covers the main behavior, merge semantics, re-render side effect, and preview mode for a complex 13-parameter mutation tool with no output schema. It references the 'same compile-and-test gate as create' without detailing that gate, and does not describe the normal non-preview return, leaving minor gaps.

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 54%, so the schema already documents several parameters including files, preview, previewFrame, previewProps, token, projectId, and compositionId. The description restates the merge behavior for files and preview behavior but adds little new meaning for the remaining parameters such as fps, width, height, and durationInFrames.

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: updates a motion composition's TSX files and/or manifest, listing name, duration, and schema. The merge clause distinguishes it from create_motion_composition without requiring the agent to open either 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?

Clear context for when to use it: merging files over an existing set, and previewing with preview:true. It does not explicitly say 'use create_motion_composition for new compositions' or name exclusions, so it stops short of full alternative routing.

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