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

Goes well beyond the annotations by disclosing the required Authorization: Bearer sb_live_... operator key on the HTTP call, that only Pix is supported, and the responsibility split (holder pays and does the videoconference; the agent never pays). It adds real operational context the annotations (readOnlyHint=false, openWorldHint=true) do not convey. Minor gap: it does not reconcile the schema's idempotency_key (24 h dedupe) with the idempotentHint=false annotation.

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?

Front-loads the purpose in the first sentence and keeps each following sentence to a distinct load-bearing point (Pix-only, pre-call confirmation, auth header, payment responsibility). Slightly dense and the parenthetical detail adds length, but nothing is wasted or redundant with the schema.

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 12-parameter mutation tool with no output schema, the description helpfully characterizes the return payload (Pix artifacts + tracking link) and the auth prerequisite. Combined with 100% schema coverage, an agent has what it needs; only the idempotency nuance is left implicit vs the schema's idempotency_key.

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 description coverage is 100%, so every one of the 12 parameters is already documented inline (CPF, CNPJ, IBGE code, product_slug source, idempotency_key behavior). The description adds only a general 'confirm produto, preço, requisitos e dados' prompt, which does not extend meaning beyond the schema. Baseline 3 applies when the schema does the heavy lifting.

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 ('cria um pedido de certificado em nome do titular') and explicitly lists what it returns (Pix QR Code copy-paste, image, validity, tracking link). This distinguishes it cleanly from the read-only siblings (get_order_status, get_product, search_products), which none of them create orders.

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?

'Antes de chamar, confirme com o titular produto, preço, requisitos e dados' gives a clear precondition before invocation, and 'Pix-only' bounds the payment method. It does not name explicit alternatives or when-not-to-use cases, but for a dedicated create endpoint there is no competing sibling to route between, so the guidance is solid though not exhaustive.

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