Prepare a contract WRITE for the user to sign. Returns an UNSIGNED transaction, its simulation, a human-readable summary, an abi.ninja signing deeplink, and warnings. IMPORTANT: this tool NEVER signs or broadcasts. Present the summary + simulation + warnings to the user and hand them the deeplink...
AI agents use prepare_tx to create or update resources in Gulltoppr — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Gulltoppr environment.
| Parameter | Type | Required | Description |
|---|---|---|---|
args | array | — | Function arguments, in order. Pass uint values as decimal strings. |
from | string | Yes | The sender address (the user's wallet). No key is needed — nothing is signed. |
chain | string | Yes | Chain alias ("ethereum", "base", "optimism", "arbitrum", "polygon", "local") or numeric chain id. |
value | string | — | Native value in wei (decimal string), for payable functions. |
address | string | Yes | 0x contract address. |
rpc_url | string | — | Override RPC URL. Required for chains with no default (e.g. local/31337). |
function | string | Yes | Function name, or full signature like "transfer(address,uint256)" if overloaded. |
Parameters from the server's own tool schema.
This tool prepares but does not execute or sign blockchain write transactions. It creates transaction data that will modify contract state when signed and broadcast by the user.
From the tool's definition Tool name 'prepare_tx' and description states 'Prepare a contract WRITE' and 'Returns an UNSIGNED transaction.' The tool explicitly handles write operations ('contract WRITE') that modify blockchain state, with the user responsible for signing and…
Attacks that exploit this kind of access
Prepare a contract WRITE for the user to sign. Returns an UNSIGNED transaction, its simulation, a human-readable summary, an abi.ninja signing deeplink, and warnings. IMPORTANT: this tool NEVER signs or broadcasts. Present the summary + simulation + warnings to the user and hand them the deeplink — they sign in their own wallet. If warnings is non-empty (decompiled ABI, proxy, or a reverting simulation), surface it. It is categorised as a Write tool in the Gulltoppr MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
prepare_tx accepts 7 parameters: args, from, chain, value, address, rpc_url, function. Required: from, chain, address, function. The full parameter table on this page comes from the server's own tool schema.
Register the Gulltoppr MCP server in PolicyLayer and add a rule for prepare_tx: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Gulltoppr. Nothing to install.
prepare_tx is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the prepare_tx rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for prepare_tx. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
prepare_tx is provided by the Gulltoppr MCP server (https://mcp.gulltoppr.dev/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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