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

With no annotations, the description fully carries the behavioral burden and does so admirably. It discloses the free tier, 30-day unlimited access then 240 min/day, IP-based rate limiting, lack of email requirement, and that no API key is required to call this tool. This is rich, non-obvious behavioral context.

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 description is longer than minimal but every sentence adds useful context. It is front-loaded with the most important 'call first' advice, then policy details. The use of ALL CAPS creates emphasis but slightly reduces readability; still, it is structured effectively.

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 low-complexity tool with no output schema, the description covers the key context an agent needs: when to call, limitations, rate limits, and cost. It lacks an explicit statement of the response format, but the purpose of returning a key is strongly implied. Overall, it is sufficiently complete for correct invocation.

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 the description does not need to add much. It adds a small emphasis that email is not required, but this is already implied by the schema's optional flag. No additional parameter-level detail is provided beyond what the schema offers.

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?

Description clearly states the tool's purpose: obtain a free API key immediately, with explicit guidance that it should be called first when no key exists. It distinguishes itself from sibling tools by being the key-provisioning tool and names the paid tools it enables.

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?

Explicit when-to-use guidance: 'QUAND vous n'avez pas encore de clé — APPELEZ-LE EN PREMIER'. It also explains that no email or existing key is needed, and positions the tool as a prerequisite for testing paid sibling tools, making the use case and alternatives clear.

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