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

With readOnlyHint=false and openWorldHint=true, the agent knows this touches external state; the description usefully clarifies the critical nuance that invoking the MCP tool does not itself spend funds and instead returns a payment challenge plus the canonical paid endpoint, plus the $2.00 USDC-on-Base cost. It stops short of describing what the audit covers or returns, but the payment-flow disclosure is substantive.

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?

Two sentences, front-loaded with the most decision-critical fact (the price and payment rail), then the effect on funds and the return shape. Dense and efficient, though x402/PAYMENT-REQUIRED jargon assumes a knowledgeable reader.

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 audit tool, the definition covers cost, the no-funds-spent guarantee, and what the call returns; the output schema exists to describe return structure. The main gap is scope relative to sibling audit tools and what surfaces are actually checked.

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?

Only one parameter ('url'), documented at 100% schema coverage as 'Base URL of the machine-commerce service to audit'. The description adds no format, example, or constraint beyond the schema, so it is the standard baseline when the schema carries the semantics.

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: 'Checks machine-commerce discovery and health surfaces', which tells the agent what the audit inspects. However, it does not distinguish itself from closely related siblings such as x402.compatibility_audit, mcp.schema_audit, or openapi.quality_audit, all of which are also 'check/audit' tools.

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?

It clarifies the payment mechanics of the call itself ('does not spend funds; returns the exact PAYMENT-REQUIRED challenge and canonical paid execution endpoint'), which is useful context for deciding to invoke it. But it gives no guidance on when to choose this audit over the many sibling audit/compatibility tools, leaving that to inference.

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