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

Annotations cover readOnly and openWorld, so the bar is lower, yet the description adds genuinely useful behavioral facts the annotations lack: a per-call price of $0.01 USDC, x402 payment, and that a full cost estimate is returned before any spend. It stops short of explaining charging mechanics or failure modes if budget is exceeded.

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?

Compact and front-loaded, with the core capability stated first and cost details after. The leading "Tool plan with cost:" is mildly redundant with the name but not wasteful enough to detract.

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 paid, open-world planning tool with no output schema and no annotation detail on billing, the description does well to surface pricing and the pre-spend estimate. It remains incomplete on the budget_usd parameter and on what the returned plan looks like, leaving real gaps.

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 0% for both parameters. The description implicitly covers 'goal' via "breaks a goal into steps" but never mentions budget_usd, which is critical for a cost-planning tool where the budget cap directly shapes the plan produced.

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: breaking a goal into steps and finding the cheapest paid API per step. It also scopes the search source (this marketplace plus the whole x402 directory), but does not explicitly differentiate itself from siblings like x402_find, x402_check, or spend.

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?

"Estimated total cost before you spend anything" implies the intended context (plan before committing money), but there is no explicit when-to-use, when-not, or named alternative such as x402_find for pure discovery.

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