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

Annotations already declare readOnlyHint=false, destructiveHint=false, and openWorldHint=false, which is somewhat surprising for a pure costing computation and is left unexplained. The description adds genuinely non-structured context: the return shape ('one costed line per quantity') and the billing model ('1 credit per quantity'), which an agent needs to avoid runaway cost. It does not clarify why the operation is flagged non-read-only.

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?

Three tight sentences, front-loaded with the use case, then the exclusion, then the cost. Every clause earns its place and none is redundant with structured fields.

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?

Covers selection, output nature, and cost, but for an 8-parameter tool with nested objects (ajustements, lot_de_fabrication), no output schema, and a non-read-only annotation, the description leaves the mutation/authorization semantics and the nested parameter behavior unexplained.

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 75%, so the schema carries most parameter meaning and the baseline is 3. The description adds only the quantity range and illustrative values (50, 500, 5000) on top of the schema's minItems/maxItems, and says nothing about matiere, plan_id, ajustements, or lot_de_fabrication.

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 ('see how the unit price of the same part changes with quantity') and scopes it precisely (2 to 8 quantities). It explicitly distinguishes itself from the sibling chiffrer_piece for the single-quantity case, so an agent can route correctly without opening either 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 (comparing unit price across quantities), when-not ('Do not use for a single quantity'), and names the alternative (chiffrer_piece). Nothing about tool selection is left to inference.

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