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

With no annotations, the description carries the full burden, but it does disclose meaningful behavior: the credit cost (free vs 1 unit) tied to each mode, which is not present in the schema. It does not explain error handling, what happens if both or neither parameter is supplied, or the shape of the returned rate.

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?

A single well-formed sentence that front-loads the compute path and its free cost before the database alternative. Every clause carries information; no waste.

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?

With no annotations, no output schema, and a nested object parameter, the description covers the two input modes and their cost but omits return value shape and behavior when parameters are combined or omitted. Adequate for a simple two-mode calculation tool, but with clear gaps.

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 100%, so baseline is 3, but the description adds genuine semantic value: it clarifies that 'poste' and 'machine' are alternative (mutually exclusive) input paths via 'ou', which the schema does not state since both are optional. This resolves real ambiguity about how the two parameters relate.

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?

The description names a specific verb (calcule/lit) and resource (taux horaire d'une machine) and distinguishes two distinct modes of operation: computing from user-supplied values or reading from the database. It is clear without opening the schema, though it does not reference or differentiate from the sibling tools.

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?

The two operating paths are stated with their cost implications (gratuit vs 1 unité), effectively telling the agent which mode to choose and why. It gives clear context but stops short of explicit when-not-to-use guidance or naming sibling alternatives.

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