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

No annotations are supplied, so the description carries the full burden and does so well: it discloses the trial allowance, the 402 refusal behaviour, that it will not invent a result, and that a signed hub receipt is returned. It does not cover idempotency, retry behaviour, or rate limits once paid, leaving a modest gap for an unannotated mutation-style tool.

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 sentences, with the core action and its sourcing dependency front-loaded before the payment mechanics. The middle sentence is dense but every clause (trial allowance, receipt, 402, next_steps) earns its place.

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 tool with no output schema and no annotations, the description is substantially complete: it explains the access model, the failure mode, and the payment parameter combinations. Return-shape details beyond the signed receipt, and the meaning of max_price_usd as a pre-payment guard, are left entirely to the schema.

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 75% and the description adds real grouping semantics the schema does not: which parameters pair together for channel payment versus x402 payment, and the receipt-bearing outcome. It omits source_hub, max_price_usd, include_full_receipt and input, though the schema documents most of those itself.

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 (invoke) and resource (a capability) and anchors it to the sibling that produces the needed input ids via market_search. An agent can distinguish this from market_search itself, which only discovers rather than executes.

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?

Explains the two access modes: a small free trial allowance that returns signed receipts, then paid access via payment_channel or an on-chain x402 payment. The when-to-use context is clear, but the description stops short of explicit guidance on which payment path to prefer or how to react to the 402 beyond reading next_steps.

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