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

Well beyond the annotations, it discloses billing behavior on retry ('replaces its frame for the same price'), the 409 price-mismatch protocol, roughly one minute of latency, no charge on failure, 400 for ineligible shots, plus 402 plan_required and storage_full prerequisites. This is exactly the operational context annotations cannot carry.

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?

Front-loaded with the action and cost, then consent, pricing, retry semantics, and error codes in a tight sequence. It is dense and parenthesis-heavy but nearly every clause earns its place; the run-on flow slightly hurts readability.

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-parameter paid mutation with no output schema, the description covers pricing, consent, retry semantics, latency, all relevant error codes, prerequisites, and follow-up tools. An agent has everything needed to call it safely and correctly.

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 real meaning: credits must equal the price the user agreed to and a mismatched value returns 409 with the current price, and shot maps to a planned shot's opening frame. That goes beyond the schema's restatement of the same fields.

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 ('Draws the picture a planned shot opens on') and immediately flags the cost dimension. It is clearly distinguishable from siblings like draw_character_sheet or revise_music_video_shot by naming the planned-shot opening frame as its target.

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 when-to-use guidance ('Good for the shots that matter most (the opening, the hook); the others are made from their references as usual'), a consent prerequisite (tell the user the price, draw only after their go), and the downstream sequence (quote_music_video and create_music_video with the plan_id).

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