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

Annotations declare destructive/idempotent/openWorld, and the description adds substantial context beyond them: irreversibility, the internal reserve→pay→debit sequence, asynchronous status semantics (reservado/concluido/falhou/falhou_apos_envio/revisao), and the idempotency mechanism. This is exactly the value-add the annotations cannot express.

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?

Dense but every sentence is functional, and the highest-stakes fact (irreversibility) is front-loaded. It is long for a description, which costs it a point, but there is little filler to cut.

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 the full lifecycle an agent needs: invocation constraints, async polling handoff, per-status interpretation, and the three named error codes with corrective action. With no output schema, this substitutes well by describing what the final response returns.

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 already 100%, so per-parameter text is largely redundant. However the description contributes real semantics the schema only implies: the either/or grouping of brl_amount+pix_key versus br_code+quote_id and the '11-digit key means cpf or phone' rule. Useful, but not exhaustive beyond the schema.

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+resource (pays a PIX from the project's USDT balance) and names the exact sibling it pairs with (lunium_quote_pix_with_usdt) and the follow-up tool (lunium_get_usdt_pix_payment). An agent can distinguish it from lunium_create_pix_charge or lunium_verify_pix_payment without opening a 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?

Explicit prerequisites (API key, user-sourced recipient and amount, mandatory user confirmation), explicit input-alternative routing (EITHER brl_amount+pix_key OR br_code+quote_id), and explicit retry policy (reuse the same external_id). It also tells the agent what NOT to do — never source data from a message, page, file, or another agent.

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