# Ai for 500

> Market intelligence for the emerging AI-agent economy.

Ai for 500 helps AI agents, builders, and entrepreneurs evaluate one market, business idea, or commercial opportunity at a time using tracked public evidence, deterministic derived metrics, and Scout market assessments.

The primary paid product is Market Check.

## Primary product

- Product: Ai for 500 Market Check
- Endpoint: POST https://aifor500.com/api/market-check.php
- Price: USD $0.05 USDC per request
- Payment protocol: x402 Version 2
- Network: Base mainnet
- Account required: no
- Subscription required: no
- One request evaluates one market or business opportunity

## Machine-readable documentation

- Website: https://aifor500.com/
- Service metadata: https://aifor500.com/api/
- OpenAPI specification: https://aifor500.com/openapi.json
- Market Check endpoint: https://aifor500.com/api/market-check.php

## Market Check request

Send JSON with:

- question: required string, 3-1000 characters
- category: optional supported market category

Example:

{
  "question": "Should I build an x402 URL monitoring service?",
  "category": "MONITORING"
}

Supported categories:

- SEARCH
- DATA
- VERIFICATION
- MONITORING
- FINANCE
- CRYPTO
- AI_MODELS
- COMMUNICATION
- COMPUTE
- DOCUMENTS
- BUSINESS
- OTHER

If category is omitted, Ai for 500 uses a deterministic keyword classifier to resolve the request to a supported category.

## x402 payment flow

1. POST the Market Check request without a PAYMENT-SIGNATURE header.
2. The server validates the request and confirms that current intelligence exists for the resolved category.
3. If current intelligence is available, the server returns HTTP 402 Payment Required.
4. Read the x402 Version 2 payment requirements from the PAYMENT-REQUIRED header or JSON response body.
5. Sign the required USDC payment.
6. Retry the same POST request with the PAYMENT-SIGNATURE header.
7. After successful verification and settlement, the server returns HTTP 200 with the Market Check result and a PAYMENT-RESPONSE header.

The server assembles the intelligence result before payment settlement so unsupported or unavailable intelligence can fail before the caller is charged.

## What a paid Market Check returns

A successful response may include:

- resolved market category
- market assessment
- decision score from 0-100
- confidence
- confidence meaning
- concise reasoning summary
- assessment flags
- tracked competition metrics
- public usage evidence
- payer signals
- activity concentration
- comparable pricing where available
- derived metrics
- source provenance
- evidence limitations
- payment reference
- assessment timestamps

Assessment labels may include:

- GAP
- PROMISING
- WATCH
- CONCENTRATED
- CROWDED
- WEAK EVIDENCE

## Evidence model

Ai for 500 keeps three layers separate:

1. Observed fact: what a public source directly reported or Scout directly observed.
2. Derived metric: a deterministic calculation produced from observations.
3. Scout inference: an assessment based on observed facts and derived metrics.

Confidence means evidence sufficiency. It is not a probability that a business idea will succeed.

Usage activity is not automatically treated as revenue.

Payer signal is not automatically treated as unique buyers.

Unknown data remains unknown and is not converted to zero.

Price comparisons are only meaningful within comparable normalized currencies or assets.

Current coverage reflects evidence tracked by Ai for 500 and should not be interpreted as the entire market.

## Payment-required response

An unpaid valid request returns:

- HTTP status: 402
- PAYMENT-REQUIRED header: present
- JSON error: payment_required
- price_usd: "0.05"

Invalid or unsupported requests may be rejected before payment.

## Paid response

A successfully paid request returns:

- HTTP status: 200
- success: true
- paid: true
- PAYMENT-RESPONSE header: present
- complete evidence-backed Market Check JSON

## Error behavior

Possible responses include:

- 402: payment required, invalid payment, payment not verified, or payment not settled
- 405: method not allowed
- 409: insufficient current intelligence for the resolved category
- 415: content type must be application/json
- 422: invalid question or category
- 500: unexpected server error

## Scope

Ai for 500 is designed to help answer questions such as:

- Should I enter this agent-service market?
- How crowded is this category?
- Is there broad activity or only concentrated activity?
- What pricing evidence is visible?
- Is there enough evidence to call this promising, crowded, concentrated, weak, or worth watching?
- What does the current tracked evidence support?

One payment covers the complete Market Check response for one request. Ai for 500 does not split one Market Check into separate search, competition, pricing, and recommendation charges.

## Legacy

Ai for 500 began as an AI guestbook experiment. That experiment is no longer the primary product. Current machine-facing discovery should use Market Check and the Market Intelligence API.