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

Annotations already declare readOnlyHint/idempotentHint/destructiveHint=false, and the description reinforces this with 'Free, changes nothing' — consistent, not contradictory. It goes further by enumerating what the call returns (clip length and frame size, per-model read costs, transcript add-on cost, and payer resolution), which is valuable since no output schema exists.

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 core action ('Measure a video clip and price...') before elaborating on outputs. The dense middle sentence listing return values is information-rich rather than padded, though it is long enough to test 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?

No output schema exists, so the description carries the return contract — length, frame size, per-model costs, transcript cost, payer/coin balance — and it does so thoroughly. Combined with the safety annotations, an agent has everything needed to call and interpret it.

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?

With a single parameter and 100% schema description coverage, the schema already documents video_url fully (https direct link, ≤300s). The description adds no format, size, or sourcing detail beyond that, so baseline 3 applies.

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 specific verbs (measure, price) on a specific resource (a video clip broken into a shot list), which is clearly distinct from the sibling start_breakdown, get_breakdown, and label_breakdown. An agent can tell immediately this is the non-committing pricing/estimation step.

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?

Ends with an explicit routing instruction, 'Use before start_breakdown,' placing it correctly in the workflow ahead of the actual breakdown. It gives clear context but names no when-not conditions or other alternatives (e.g. when to skip straight to start_breakdown).

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