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

Substantially exceeds what annotations provide: pricing depends on video length, a backup-model fallback may raise cost up to a quoted ceiling, allowance plans do not apply, and the two-step confirmation protocol is spelled out. These are cost/authorization behaviors an agent cannot infer from destructiveHint=true or openWorldHint=false.

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?

Purpose is front-loaded in the first clause, followed by cost, confirmation, and return-value handling in a logical order. Slightly dense in the billing region ('Spends the user's coins... charged in VerseIn coins... allowances do not apply'), where two sentences could be tightened into one without losing information.

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 cost-incurring mutation with an output schema, the description covers the critical unknowns: billing, confirmation, idempotent retry framing, and follow-up task polling. It omits nothing blocking, though it says nothing about failure/refund behavior when a job errors after charging.

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 baseline is 3, but the description adds cross-parameter meaning the schema cannot: the relationship between the quoted ceiling (max_total_coins), the confirmation threshold, and the returned confirmation_token as a retry loop. It also frames preset/prompt/reference as mutually alternative control modes.

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 the lighting of a video') and enumerates the three input modes (preset, text direction, reference image), which cleanly separates it from relight_image and edit_video. An agent can identify the tool's job without opening the 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?

Gives explicit operational context: when a ceiling exceeds the threshold the call returns needs_confirmation, the agent must ask the user, then retry with the token; results are followed via get_tasks. It does not explicitly contrast with relight_image or edit_video, 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.