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

Annotations already declare destructiveHint=true and idempotentHint=true, so the safety profile is covered; the description still earns credit by disclosing the actual mutation model — per-path file replacement, omitted files retained, and prop values preserved when the schema changes. That directly answers what gets destroyed versus kept, which the annotations alone could not.

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?

Three short sentences, front-loaded with the action, and every clause carries distinct information about partial-update behavior. No filler or restatement of the name.

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 9-parameter destructive mutation with no output schema, the description covers the parts an agent is most likely to get wrong (file replacement and schema migration). It could still note that unspecified scalar fields are untouched or what the call returns, but with annotations carrying destructiveness and idempotency it is close to complete.

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 only 22%, so the description must carry the load; it does explain the two non-obvious parameters — `files` as a path-to-content map and `schema` as a partial migration — which is high-value. The six remaining scalars (fps, name, width, height, durationInFrames, plus the required token) get no mention, leaving a real compensation gap.

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 ("Edits an existing composition") and immediately clarifies the semantics of the edit (per-file replacement, schema-preserving). It is clearly distinguishable from create_composition, though it does not name any sibling 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?

Usage is implied rather than stated: "edits an existing composition" tells an agent this is for modifying, not creating, and "files not sent are kept" signals partial-update semantics. But nothing directs the agent away from set_props for prop changes or toward create_composition for new compositions, and no prerequisites (token, active vs. explicit id) are given.

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