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

The description adds a meaningful behavioral trait beyond the sparse annotations: 'Uses this month’s generation allowance.' This tells the agent the operation consumes quota, which is not disclosed by readOnlyHint, openWorldHint, or destructiveHint. It does not contradict any annotation.

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 short sentences, front-loaded with the action and followed by the key cost side effect. Every word earns its place, with no filler or repetition of schema content.

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 tool with four documented parameters and an output schema, the description covers the essential purpose and the main side effect (allowance consumption). It is slightly thin on explicit sibling routing, but the schema and output schema fill most remaining 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 100%, so all four parameters (game, quoteId, themeKey, customWorld) are already documented. The description adds no parameter-level detail, but it does not need to; the baseline of 3 is appropriate because the schema carries the semantic load.

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?

The description states a specific verb and resource: 'Start a Last Frame run and film the opening shot.' This clearly differentiates the tool from siblings like end_last_frame_clip, timeout_last_frame, and type_last_frame without needing to inspect their 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?

The purpose implies usage: this is the tool to start a Last Frame run, not to end, choose, or time one out. However, it never explicitly names alternatives or gives when-not-to-use guidance, so an agent must infer routing from the tool name and sibling list.

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