Universal Crypto MCP

ucai_sponsor_gas

Sponsor gas costs for users' smart contract transactions via x402, enabling them to transact without holding network tokens. Works across EVM chains.

Instructions

Sponsor gas for a user's smart contract transaction. The AI agent pays for gas using x402 payment. Fee: 0.10% of gas cost + gas cost in USD.

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": {
      "userAddress": "<userAddress>",
      "contractAddress": "<contractAddress>",
      "functionName": "<functionName>",
      "args": "<args>",
      "abi": "<abi>"
    },
    "name": "ucai_sponsor_gas"
  }
}

Input Schema

Name	Required	Description	Default
`abi`	Yes	Contract ABI
`args`	Yes	Function arguments
`network`	No	The blockchain network to use	arbitrum
`maxGasUsd`	No	Maximum gas in USD to sponsor (default: $5)
`userAddress`	Yes	User's wallet address
`functionName`	Yes	Function to call
`contractAddress`	Yes	Target contract address

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Aug 8, 2026

TDQS

A3.5/5.0

Behavior3/5

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

The description discloses that the AI agent pays for gas and details the fee (0.10% + gas cost), which is critical financial context. However, it does not mention the transaction outcome, failure handling, or reversibility. With no annotations, this leaves some gaps in transparency.

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 two concise sentences with the core purpose front-loaded. It includes the fee and payment mechanism without any redundant or fluff content.

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

Completeness3/5

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

The description explains the financial cost and fee, which is essential for a gas-sponsoring tool. However, it does not describe the expected return (e.g., transaction hash) or any failure conditions, making it adequate but not fully complete for a financial transaction 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?

The input schema has 100% parameter description coverage, so the baseline is 3. The description adds no new parameter-specific meaning beyond what the schema already provides, though it reinforces the purpose of the key parameters (contract details, arguments, ABI).

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 clearly states the action: sponsoring gas for a user's smart contract transaction, and mentions the payment method (x402) and fee structure. However, it does not explicitly distinguish itself from the sibling tool 'ucai_estimate_gas_sponsorship', which likely handles cost estimation rather than execution.

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 usage when the AI agent needs to pay gas on behalf of a user but gives no explicit guidance on when to use this tool versus alternatives like estimation or direct transaction tools. No exclusions or prerequisites (e.g., x402 balance) are mentioned.

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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