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

Goes well beyond the sparse annotations: it discloses that the request is real but executed against sandbox keys, that the response includes status code and Request-Id, that stamping uses the SAT test issuer, and that there is no cost. This also resolves the destructiveHint=false question by making explicit that nothing production-side is touched.

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, front-loaded sentences with essentially no filler; the sandbox-key constraint and the no-cost stamping note each carry real information. Slightly more compact phrasing could still be achieved.

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?

No output schema exists, and the description covers the return shape (code, Request-Id, JSON), the credential requirement, and the sandbox semantics. Rate limits and pagination behavior for the proxied endpoint are the only notable omissions.

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?

With 80% schema description coverage, the schema already explains path, body, api_key and idempotency_key. The description reinforces what body is for (trying a payload) but adds no format or constraint detail beyond the schema, so the baseline 3 applies.

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 (makes a real API request) plus scope (test mode, fk_test_ keys only) and the return payload (status code, Request-Id, JSON). It implicitly separates itself from the doc-oriented siblings by making clear this actually executes a call, though it never names an alternative tool.

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?

"Para probar un cuerpo antes de escribir el código" gives a concrete use case, and "nunca una fk_live_" plus the instruction to ask the person for their key set hard boundaries. It stops short of naming when to prefer describe_operation or explain_error instead.

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