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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds traits beyond that: the estimate is bound to the draft graph that run_pipeline executes, the quote is single-use and invalidated by pipeline edits, and a preview render path exists. These are real behavioral constraints (staleness, quote lifecycle) that annotations do not cover.

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?

The core purpose is front-loaded in the first sentence and the sentences are substantive. It is on the long side, with parenthetical asides about client panels and the Veo 3.1 Lite preview, but nearly all of it is actionable guidance rather than filler.

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, yet the description fully accounts for the return surface (`lines`, `cheaper`, `preview`, `quoteId`) and the workflow that consumes it. For a tool whose main risk is misusing the quote downstream, the definition is complete enough to call and sequence 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 0% for the single pipelineId parameter, so the description must carry the load. It contextualizes the parameter by stating the estimate runs against the draft graph run_pipeline executes, which implies pipelineId references a pipeline, but it never explicitly defines the parameter, its format, or draft-vs-published resolution.

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: estimate the credit charge of one pipeline run, including the breakdown (`lines`) and balance coverage. It also enumerates the return facets (`cheaper`, `preview`, `quoteId`) and contrasts with the actual execution path (run_pipeline), so an agent can distinguish it from siblings like get_credit_balance and run_pipeline without opening a 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 when-to-use ('call this before running a pipeline you built or changed in this conversation'), the required human-in-the-loop step (tell the person the price and wait for go-ahead), and the downstream contract (pass quoteId to run_pipeline). It even names the failure mode (run_pipeline refuses if the pipeline changed) and tells the agent to re-estimate.

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