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

Annotations already declare the write/non-destructive/idempotent profile, and the description adds real context on top: the edit produces a new revision while the earlier revision is left untouched (explaining why destructiveHint is false), matching is substring-based on text layers, and the call is free of credit cost. Cost and revision-persistence behavior are not derivable from the structured fields.

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, mutation scope front-loaded before the no-op caveat and the cost note. Every sentence carries information; the only drag is the slightly garbled 'gets replace' and an unexplained 'Free of credits' phrasing that could be stated more plainly.

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 3-required-param mutation tool with full schema coverage and no output schema, the description covers scope, persistence semantics, cost, and the no-op case. It never says what the call returns (e.g., the new revision identifier), which is the one detail an agent might need since there is no output schema.

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 the schema already documents film, revision, and the find/replace pairs and their ordering. The description still adds matching semantics not in the schema — that 'find' matches text layers whose words contain it (substring, not exact) — which materially affects how an agent constructs the replacements array.

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 (change text in a film) and then sharpens scope: every text layer whose words contain 'find' gets replaced. It even distinguishes itself from the sibling ugcfans_make_launch_film by noting those films have no text layers, so an agent can tell them apart without opening schemas.

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 when-not condition: films produced by ugcfans_make_launch_film are effectively no-ops for this tool. It also implies the operation is a non-in-place edit that yields a new revision. It does not name an alternative tool for other kinds of film edits, so it stops short of a full when/when-not/alternatives treatment.

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