Why APIbase
One MCP + REST endpoint to APIbase's live tool catalog (counts: apibase.pro/llms.txt). No signup, no subscription, no API key to start — pay per call in USDC (x402 on Base or MPP on Tempo).
An agent that needs an external capability goes through the same four steps regardless of which provider ends up serving the call: it has to discover that a tool exists, evaluate whether it fits (price, schema, availability), pay for it, and execute the call. APIbase is built around making all four steps happen against one endpoint instead of one per provider.
1. DISCOVER
Call the apibase.discover MCP tool, or GET /api/v1/discover?intent=... over plain REST — both free ($0), no authentication required.
GET https://apibase.pro/api/v1/discover?intent=search+flights&max_price_usd=0.01
Discovery ranks by relevance, then quality, then price, and returns each match's pricing, payment rails, availability, and quality signal in the same response. The full catalog is also fetchable directly at /api/v1/tools if an agent prefers to cache it and search client-side.
2. EVALUATE
Every tool entry an agent gets back carries what it needs to decide whether to call it, before spending anything:
pricing.price_usd— the sticker price for that specific calltier— micro / standard / premium, so an agent can filter by wallet sizeinput_schema— JSON Schema for the call body, so params can be validated before sendingmin_balance_usd— the balance a wallet should hold before attempting the call
Nothing here requires trusting a third-party listing — it's the same JSON the live server returns to any HTTP client, checkable at /api/v1/tools right now.
3. PAY
A priced tool call without a payment header gets back an HTTP 402 challenge naming the exact price and rail options. Two independent rails are accepted on the same endpoints — an agent picks whichever matches its wallet:
| Rail | Network / asset | Header |
|---|---|---|
| x402 | USDC on Base mainnet | X-PAYMENT |
| MPP | USDC on Tempo mainnet | Authorization: Payment |
Neither rail requires a prior signup step: a correctly signed first payment is enough to create agent credentials, so there is no dashboard, no email, no approval queue between "I found the tool" and "I called it." Full mechanics: /connect.
4. EXECUTE
tools/call (MCP) or the equivalent REST call runs the request against the upstream provider. Payment is escrow-first and the call is idempotent by design; a failed provider call is never billed — only a delivered response is charged. If the call fails outright, the error response is the signal an agent needs to decide whether to retry or fall back to reading a different tool's docs — APIbase does not silently substitute a different provider's response for the one that was requested.
How this compares by class
Not every agent-facing surface that looks similar solves the same problem. Comparing by class, not by name, because that comparison is what's actually settled today:
| Class | What you connect to | Before the first paid call |
|---|---|---|
| Single MCP server | One provider's own tools | Usually nothing, for that one provider's read-only tools — but it's still only that one provider |
| MCP marketplace / registry | A directory listing of other people's MCP servers | You still connect to, and often authenticate against, each listed server separately |
| API marketplace (REST) | A directory of individual REST APIs | Signup and an API key per provider, sometimes a signup for the marketplace itself too |
| Unified gateway with signup | Multiple providers behind one endpoint | Signup and an API key for the gateway |
| APIbase | Multiple providers behind one MCP + REST endpoint | Nothing — the first paid call creates agent credentials automatically |
This table describes categories of tooling, not any specific named product.
Answers for specific needs
The DISCOVER/EVALUATE/PAY/EXECUTE loop above is generic. These pages answer specific capability needs directly, naming the tools that exist for them today: