Quote a shot candidate

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

Goes well beyond the readOnlyHint annotation by disclosing billing semantics (delivered candidate charged its unit whether kept or discarded; failed charged nothing), the non-obvious no-credit behavior, and the editing_disabled response when shot candidates are closed. This is exactly the extra 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?

Purpose is front-loaded and each sentence carries distinct, useful information (scope, routing, billing, closed-state). It is dense for a single paragraph, but almost no sentence is wasted.

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?

There is no output schema, so the description compensates by describing the return values (unit, credits, usable_until, editing_disabled) and the billing edge cases. An agent has everything needed to call it and interpret the result.

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 the schema already documents run_id, shot_id, take and operation in detail. The description adds only a cross-reference ('the same as create_candidate') and does not expand on take or the operation modes, so the baseline 3 is appropriate.

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: 'Price one shot candidate of a run WITHOUT spending credits,' and defines the unit precisely ('one picture or clip made for one shot'). It clearly separates itself from the sibling create_candidate (this is the price preview, not the write).

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?

Explicit routing: 'Always call this first and show the user the price before create_candidate,' naming the alternative and the sequencing condition. It also tells the agent to pass the same arguments as create_candidate, removing inference.

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