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

facilitator_fit_precheck

FREE headline pre-check (100/day per wallet; pass caller). Returns assessability only - whether the submission is well-formed; no fit state 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>",
      "network": "<network>",
      "scheme": "<scheme>",
      "facilitator_url": "<facilitator_url>"
    },
    "name": "facilitator_fit_precheck"
  }
}

Input Schema

Name	Required	Description
`payTo`	No	Optional seller wallet; required for the PayAI free-credits leg when the named facilitator is PayAI.
`caller`	Yes	Solana base58 wallet of the operator; keys the free allowance (100/day per wallet).
`scheme`	Yes	The challenge scheme (e.g. exact).
`network`	Yes	The challenge network (e.g. solana, base).
`facilitator_url`	Yes	The facilitator base URL whose /supported is graded; the host is reported, the path is never stored.

Schema Changelog

Changes observed during successful MCP inspections.

AddedNov 3, 2026

TDQS

A3.7/5.0

Behavior4/5

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

With no annotations, the description carries the full burden and does meaningful work: it discloses that the call is free, that the allowance is 100/day per wallet and keyed to `caller` (so calling consumes quota), and critically that no fit state is returned. It stops short of covering idempotency, failure modes, or what 'assessability' output looks like, which keeps it below 5.

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 short sentences, front-loaded with the cost and quota hook followed by the output-scope caveat. The parenthetical 'pass caller' is slightly tacked-on and largely duplicates the schema, but there is no wasted prose overall.

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?

No output schema exists, yet the description explains what the tool does and does not return, and it flags the rate-limit/cost model an agent needs before calling. What remains thin is the concrete shape of the result and behavior on malformed submissions, but the essentials for correct invocation are present.

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 five parameters are already documented, including caller's role in keying the free allowance. The description adds only the redundant 'pass caller' reminder and nothing about scheme/network/facilitator_url semantics, so the baseline 3 applies.

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 capability — a free, headline-level pre-check of a facilitator submission — and states its scope precisely ('assessability only... no fit state is returned'). That negative clause implicitly separates it from facilitator_fit_check, though the sibling is never named outright.

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 word 'pre-check' plus 'FREE headline pre-check' and the 100/day wallet quota imply this is the cheap first pass before facilitator_fit_check, and the guidance to pass `caller` supports that. However, no explicit when-to-use/when-not statement or named alternative is given, so an agent must infer the routing from the tool name prefix.

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

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

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