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

Annotations declare readOnlyHint=false, idempotentHint=false, destructiveHint=false, so the write nature is already structured. The description adds genuinely new behavior: it explains the return value ('dollar value at public list prices; unknown stays null'), which matters because there is no output schema. It does not say whether submissions can be overwritten or re-sent.

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 dense sentences with the required parameter and the simple mode front-loaded, then the measured-comparison variant. Nothing is repeated from structured fields, though the telegraphic style ('Optional, for the person') costs a little 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 9-parameter write tool with nested objects and no output schema, the description covers most of the calling contract and explains the return, which is good. It still leaves 'provider' unexplained and the nested baseline/actual sub-fields undefined, so an agent could not populate every field confidently.

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 0% across 9 parameters, so the description has to compensate. It does name model, estimated_tokens_saved, task_id, baseline_id, baseline, actual, whole_task:true and execution_ref, and groups them into two coherent modes. But it omits 'provider' entirely and gives no shape for the nested input/cached_input/output objects, leaving real gaps.

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: report your model id plus an estimate of tokens saved, and get back a dollar value. That is a clear action an agent can distinguish from a read-only listing. It never names the sibling 'savings' tool, so the boundary between reporting and reading savings data is left implicit.

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?

'Optional, for the person' signals this is a voluntary submission, and the second sentence implicitly defines two modes (simple estimate vs. measured comparison). However, it never states when an agent should prefer this over the sibling 'savings' tool, nor what prerequisites or consequences submitting has.

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