ExchangeRebel — pay-per-call APIs for AI agents (x402 on Solana)

validity_check_precheck

FREE headline pre-check (100/day per wallet; pass caller). Returns assessability only - whether the submission is well-formed; no ceiling or window verdict is returned.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "caller": "<caller>"
    },
    "name": "validity_check_precheck"
  }
}

Input Schema

Name	Required	Description
`caller`	Yes	Solana base58 wallet of the operator; keys the free allowance (100/day per wallet).
`payload`	No	The one signed-payload descriptor whose validity window is evaluated: rail plus its validity fields (e.g. valid_before for EVM).
`challenge`	No	The one upto challenge: scheme, network, payTo, asset, max_amount_required (the ceiling), asset_decimals.
`evaluation_at_unix`	No	The evaluation instant, unix seconds. The window is evaluated at this instant, never at a hidden clock.

Schema Changelog

Changes observed during successful MCP inspections.

AddedNov 3, 2026

TDQS

A3.5/5.0

Behavior3/5

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

With no annotations, the description carries the full burden and does disclose meaningful traits: free tier, 100/day per wallet quota keyed to caller, and the crucial negative scope that no ceiling or window verdict is returned. It stops short of quota-exceeded behavior, whether the caller needs any authentication, or error semantics, which matter for a quota-limited tool.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Two compact sentences with the cost/quota signal front-loaded and the output limitation stated second. Every clause carries information and there is no filler, minor jargon ('headline', 'assessability') aside.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

There is no output schema, so the description must carry the return-value burden, and it does so by defining the result as assessability only and explicitly excluding ceiling and window verdicts. Combined with a fully documented schema, that is nearly sufficient; only quota-exceeded and error behavior are unaddressed for a nested-object, quota-gated tool.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so all four parameters are already documented in the schema, and description adds no new syntax or format detail. The only reinforcement is 'pass caller' and '(100/day per wallet)', which restates the caller parameter's purpose rather than extending it, making the baseline 3 appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description names a specific verb (pre-check) and states exactly what is produced: assessability only, no ceiling or window verdict. That cleanly distinguishes it from the siblings that do return verdicts (validity_check_validity, validity_check_upto), though those siblings are never named, so the agent must infer the split itself.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies a cheap pre-flight role ('headline pre-check', 'assessability only') and rules out verdict use, which is useful implied guidance. But it never explicitly says when to use this instead of validity_check_validity or validity_check_upto, nor what to do after a passing assessability result.

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

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