AI agents call decode_tx to retrieve information from Gulltoppr without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
| Parameter | Type | Required | Description |
|---|---|---|---|
chain | string | Yes | Chain alias ("ethereum", "base", "optimism", "arbitrum", "polygon", "local") or numeric chain id. |
rpc_url | string | — | Override RPC URL. Required for chains with no default (e.g. local/31337). |
tx_hash | string | Yes | 0x… transaction hash. |
Parameters from the server's own tool schema.
This tool decodes and interprets transaction data (calldata and execution trace) without performing any on-chain actions, modifications, or side effects. It is a read/analysis tool that retrieves and interprets existing blockchain data. No signing required, no state changes possible.
From the tool's definition "Decode what a transaction did: decoded calldata (and trace when available)" — purely analytical/read operation on existing transaction data
Attacks that exploit this kind of access
Decode what a transaction did: decoded calldata (and trace when available), via heimdall. It is categorised as a Read tool in the Gulltoppr MCP Server, which means it retrieves data without modifying state.
decode_tx accepts 3 parameters: chain, rpc_url, tx_hash. Required: chain, tx_hash. 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 decode_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.
decode_tx is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the decode_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 decode_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.
decode_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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