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

With no annotations, the description carries the disclosure burden. It adds meaningful behavioral context: paid ($0.01 USDC Base x402), uses indicative CGI rates, and excludes tax ruling authority. It does not state response format or error behavior, but for a simple converter this is minor.

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 short sentences, front-loaded with the core purpose, then the required parameter rule, then caveats. No filler or repetition.

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?

The tool is low complexity, and the description covers purpose, rate basis, parameter constraint, payment, and limitations. It does not explicitly state the output shape, but conversion output is reasonably inferable from HT ↔ TTC.

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?

The input schema only permits additionalProperties and defines no parameters, so the description's naming of amount_ht and amount_ttc plus the exactly-one constraint is essential and fills the schema gap. It does not detail numeric formats or currency, but gives enough to call correctly.

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 conversion (French HT ↔ TTC) with a verb and resource, and enumerates the exact rate tiers (20/10/5.5/2.1/0). This clearly identifies what the tool computes and distinguishes it from rate-list or VAT-rule siblings.

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?

Explicitly instructs to pass exactly one of amount_ht or amount_ttc, which is the key usage rule. Adds a 'Not a tax ruling' exclusion, though it does not name a specific alternative sibling for when tax advice is needed.

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