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

No annotations are provided, so the description carries the full burden. It does disclose real behavioral context: the call costs $0.025 USDC, is paid via x402, and settles on Base mainnet — material for an agent deciding whether to invoke. Beyond that it says nothing about what the operation reads or computes, latency, idempotency, or failure modes.

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 short sentences, purpose front-loaded before the payment detail. Nothing is padded or repeated, though the payment sentence is the only thing standing in for all missing operational guidance.

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?

A five-parameter, unannotated tool with no output schema and no parameter documentation needs a description that at least sketches the inputs and the decision shape. The description omits both, leaving only the pricing model; an agent cannot construct a valid call from this definition alone.

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?

Five parameters (input, budget, endpoint, candidates, required_fields) with 0% schema description coverage and untyped/empty schemas. The description mentions none of them, so an agent has no idea what 'input', 'candidates', or 'required_fields' should contain. With coverage this low the description had to compensate and does not.

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 artifact: 'produce a machine-readable purchase eligibility decision.' That is clearer than a generic name restatement, and 'purchase eligibility' is distinct from sibling names like service_verify or delivery_verify. It never explicitly contrasts itself with the free siblings, so sibling differentiation is left to inference.

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?

Only guidance is the price line, which implies this is a paid call, but there is no statement of when to use this versus free_diagnostic, service_verify, service_compare, or delivery_verify. No prerequisites, no exclusions, no ordering guidance for an agent choosing among five related tools.

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