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

Annotations only declare readOnly=false, idempotent=true, destructive=false; the description goes well beyond them, disclosing the 402-price response, the x402 v1 body vs v2 PAYMENT-REQUIRED split, balance custody rules (account/credit holder vs the x402-confirming wallet), the mmw_… credential flow via wallet_start/wallet_token, and 30-day plan vs 90-day package validity with no auto-renewal. It stops short of describing the success response body, which is the main remaining gap.

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?

Purpose is front-loaded in the first sentence, but the remainder is a dense, run-on block where several clauses (credential retrieval, custody of balance, expiry windows) are compressed into single sentences and require re-reading. Each fact is relevant, but the sequencing mixes response format, identity semantics, and duration rules without clear structure.

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 payment tool with no output schema and four interacting auth modes, the description covers the failure path, credential acquisition, and validity periods, which is substantial. It leaves the successful purchase response and how the resulting lookup quota is consumed undocumented, which an agent would need before calling.

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 parameter (compra, oferta, payment, credit_token) is already documented, and the description adds no syntax or format detail for any of them. It does reinforce the idempotency semantics of the repeat-with-same-mark behavior at the conceptual level, which aligns with the schema, but the schema is doing the work.

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 and resource: buys the single package or one of the three plans, and names both payment rails (credit or x402) plus the no-account case. It never names a sibling (e.g., consulta_planos for browsing, api_access_buy for API access), so the boundary with adjacent tools is left implicit, but the purchase action itself is unambiguous.

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?

Usage is implied rather than stated: the mention that an unpaid call returns 402 with the price implies you should call this to obtain a quote, and that offers come from a prior lookup. There is no explicit when-to-use vs. when-not, no pointer to consulta_planos or pricing as the way to discover offers, and no guidance on choosing credit_token vs payment.

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