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Hiroshi-Ichiyanagi

obolpay-x402-mcp

by Hiroshi-Ichiyanagi
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Python
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obolpay-x402-mcp

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📖 Tutorial: Let your AI agent autonomously buy data — x402 + gasless prepaid + MCP on Base

MCP server for the live Obolpay x402 gateway — pay-per-call premium data for AI agents, settled in USDC on Base mainnet via HTTP 402.

Give any MCP-compatible agent (Claude Desktop, etc.) the ability to discover → evaluate (free preview) → pay once → then call GASLESS forever → verify a signed receipt — autonomously.

🚀 Copy-paste examples (start here) → examples/

No MCP needed to try it. Zero setup, no wallet, stdlib only:

python3 examples/quickstart_preview.py   # evaluate the data QUALITY for free (trustless preview)

Then buy today's verifiable openunit value with one signed USDC micropayment (buy_openunit.py), or drop it into a LangChain/any-LLM agent as a tool (agent_tool.py). Full walkthrough: examples/README.md.

Related MCP server: @true402.dev/mcp-server

Tools

Tool

What it does

discover()

Machine-readable service manifest (price, token, network, capabilities)

preview()

Free data sample + price from the 402 challenge (no spend)

purchase()

One-shot on-chain pay-and-fetch

topup(tx_hash)

Fund a prepaid balance from a USDC deposit (once)

balance(address)

Balance, calls remaining, next nonce

spend_gasless()

Instant, gasless pay-per-call from the prepaid balance (no on-chain tx/gas)

verify_receipt(message, signature)

Third-party verify a proof-of-purchase receipt

Why it's different

  • Free preview before paying — evaluate the data, no blind spend.

  • Prepaid GASLESS balance — deposit USDC once, then unlimited cheap calls via off-chain signed vouchers.

  • Signed receipts — EIP-191 proof-of-purchase, verifiable at /verify-receipt.

  • Freshness SLA + auto-refund — stale data is auto-refunded to your balance.

  • Delta delivery (X-Since-Seq) — only new items, saves your context tokens.

Run

pip install -r requirements.txt          # mcp[cli], web3, eth-account, requests
export X402_AGENT_PRIVATE_KEY=0x...       # a Base wallet with USDC + a little ETH for gas
# optional: export X402_BASE_URL=https://x402.obolpay.xyz   (default)
python x402_mcp_server.py

Claude Desktop (claude_desktop_config.json)

{
  "mcpServers": {
    "obolpay-x402": {
      "command": "python",
      "args": ["/absolute/path/to/x402_mcp_server.py"],
      "env": { "X402_AGENT_PRIVATE_KEY": "0x..." }
    }
  }
}

Links

Built on x402 + Base. USDC micropayments for the AI agent economy.

Available Tools

1 tool
topupA

Credit a prepaid balance from an on-chain USDC deposit to the recipient. First send USDC to the recipient on Base, then call this with the tx_hash.

ParametersJSON Schema
NameRequiredDescriptionDefault
tx_hashYes

TDQS

A4/5.0
Behavior2/5

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It mentions the action (credit) and the prerequisite, but does not disclose behavioral traits such as whether the operation is destructive, rate limits, error handling for invalid tx_hash, or any idempotency guarantees. More detail would be beneficial.

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

Conciseness5/5

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

The description is extremely concise with two sentences. The main action is stated first, followed by the prerequisite and input instructions. No superfluous words; every sentence adds necessary information.

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?

Given the tool's simplicity (one parameter, no output schema, no annotations), the description covers the essential aspects: what it does, when to use it, and what input is required. It lacks information about the return value or possible errors, but the context is mostly sufficient for an agent to decide and invoke correctly.

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

Parameters4/5

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

Schema description coverage is 0%, but the description compensates by explaining the meaning of tx_hash: the transaction hash from the on-chain USDC deposit. This adds significant value beyond the schema's minimal 'Tx Hash' label, though it could be slightly more explicit about the format or source.

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

Purpose5/5

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

The description clearly states the specific action (credit a prepaid balance) and the resource (from an on-chain USDC deposit to the recipient). It distinguishes the tool's purpose by outlining the prerequisite steps, making it unambiguous even without sibling tools.

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

Usage Guidelines4/5

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

The description explicitly tells when to use the tool: after sending USDC to the recipient on Base. It provides a clear prerequisite and indicates the required input (tx_hash). However, it does not discuss when not to use it or mention alternatives, though the tool is single-purpose.

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

Tool Schema Changelog

Recent tool additions, removals, and schema changes observed during successful MCP inspections.

  1. 1 tool updatev1.0.0
    • First observedtopup
Deploy Server
One endpoint for every MCP toolRayrun runs every MCP server behind one URL and holds the credentials. Each call is decided per client, tool, and argument, then recorded.ray.runAd

TDQS

A3.9/5.0

Scored across 1 tool

Disambiguation5/5

Only one tool exists, so there is no risk of confusion or overlapping purposes.

Naming Consistency5/5

With a single tool, naming consistency is inherently maintained; the name 'topup' is concise and action-oriented.

Tool Count2/5

A single tool is insufficient for a payment-related server; essential operations like checking balance or initiating deposits are missing.

Completeness2/5

The tool requires prior on-chain USDC transfer but provides no tool for that step, leaving a critical gap in the workflow.

Maintenance

ActivityMaintained
ResponsivenessNo issues

Resources

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