Uniswap Universal Router Decoder

Name: Uniswap Universal Router Decoder
Author: Elnaril

by Elnarilversion 4.0.0i★ –iRuns on your computer

Registry nameio.github.Elnaril/uniswap-universal-router-decoder

Install

Overview

Description from the maker (original English)

Decode and encode Uniswap Universal Router calldata (V2, V3, V4). Read-only: never signs or sends.

PopNx MCP’s three pillars

These three are never merged into one score: opinions, measurements and popularity are different things.

User voiceiNo reviews yetReviews open together with accounts in a later step
Our basic checksi1 of 1 passedChecked from public information; code not scanned yet
UsageiNot measured yet★ –

What you can do with it

We have not written a plain-language summary for this one yet. Below are the facts we read from the registry.

Connection: Runs on your computer
Transport: stdio
Category: Other

Install

Pick the AI app you use, then copy the settings.

Before you install

Basic checks: 1 of 1 passed
Runs on your computer with your user’s permissions (files, network, apps).
You fill in yourself: RPC_URL

You need

PyPIPython’s uv installed (for the uvx command)

Which app do you use?

ClaudeClaude CodeCursorVS CodeChatGPT

Pick your app above. We remember it, so next time the button says “Install in …”.

Open Claude Desktop → Settings → Developer → Edit Config, and paste this into claude_desktop_config.json

{
  "mcpServers": {
    "uniswap-universal-router-decoder": {
      "command": "uvx",
      "args": [
        "uniswap-universal-router-decoder"
      ],
      "env": {
        "RPC_URL": "your-value"
      }
    }
  }
}

Run this in your terminal

claude mcp add uniswap-universal-router-decoder --env RPC_URL=your-value -- uvx uniswap-universal-router-decoder

Fill in the empty values before running it.

Open in Cursor

Or copy the settings yourself

Paste into .cursor/mcp.json in your project, or ~/.cursor/mcp.json

{
  "mcpServers": {
    "uniswap-universal-router-decoder": {
      "command": "uvx",
      "args": [
        "uniswap-universal-router-decoder"
      ],
      "env": {
        "RPC_URL": "your-value"
      }
    }
  }
}

Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.

Open in VS Code

Or copy the settings yourself

Paste into .vscode/mcp.json in your project

{
  "servers": {
    "uniswap-universal-router-decoder": {
      "type": "stdio",
      "command": "uvx",
      "args": [
        "uniswap-universal-router-decoder"
      ],
      "env": {
        "RPC_URL": "your-value"
      }
    }
  }
}

Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.

This one runs on your computer, and ChatGPT can only connect to servers on the internet. Pick another app.

Your choice stays on this device in a cookie; no account needed.

Values you fill in

RPC_URL env
Ethereum RPC endpoint. Optional: only decode_transaction needs it.

These settings are generated from the maker’s registry entry. If the README says otherwise, follow the README.

What it can do

Runs on your computer; the tool list appears in your AI app after you install it.

Basic checksi

We check information anyone can see; we have not read the code. Checks that do not apply are left out of the count. · Checked Nov 7, 2026

✓ Pass
Maker matches the repo
The registry name was verified with the GitHub account Elnaril, which owns the repo
… Not checked yet
Still maintained
We have not read this repo from GitHub yet
… Not checked yet
Has a licence
We have not read this repo from GitHub yet
– Not applicable
Endpoint responds
This one runs on your computer; there is no internet endpoint
– Not applicable
Sign-in with OAuth
Runs on your computer and uses local settings instead
… Not checked yet
No hidden instructions in tool descriptions
Runs on your computer; we can only read tool lists from internet endpoints

Compared with others in Otheri

More stars than 0% of the other 32709 servers in this category
Published to the registry more recently than 79% of the other 32709 servers in this category
Basic checks equal to or better than 100% of the other 32709 servers in this category

Compared with every active server in this category in the registry. Stars count only when the publisher owns the repo.

Common questions

Is Uniswap Universal Router Decoder safe?

It passed 1 of 1 applicable basic checks. We have not read the code. Before adding a key or token, see what access the server asks for and use a key with only the permissions you need.

What keys or codes does it need?

The registry does not list a required key, though some servers ask you to sign in on first use.

Does it run on my computer or in the cloud?

It runs on your computer. Your AI app starts it when needed, and data does not pass through the maker’s servers (unless it calls an online service itself).

Is it still maintained?

The GitHub repo last changed –, and the latest version (4.0.0) reached the registry 9 days ago.

Which apps can use it?

Apps that support MCP, such as Claude Desktop, Claude Code, Cursor and VS Code. You also need Python (uv) on your computer.

What can I use instead?

In the same category: Spec Driven Development, Remote Desktop Commander, SwarmMemo

Alternatives

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README from the maker

Open the README

Copied from the maker’s repo as written. PopNx MCP has not reviewed or endorsed it. HTML, images and scripts are removed. Links lead off this site.

Uniswap Universal Router Decoder & Encoder

Many thanks to everyone who has ☕️ offered some coffees! ☕️

or ⭐ starred this project! ⭐

It is greatly appreciated! :)

Project Information

Code Quality

Release Notes

See the release notes page

v4.0.0 - breaking changes

Update COMMAND_TYPE_MASK to 0x7f to match UR
Add support for the PAY_PORTION_FULL_PRECISION command (0x07)
Add support for the BALANCE_CHECK_ERC20 command (0x0e)
Add support for the V3_POSITION_MANAGER_PERMIT command (0x11)
Add support for the V3_POSITION_MANAGER_CALL command (0x12)
Add support for the EXECUTE_SUB_PLAN command (0x21)
Add revert_on_fail to the encoder methods for the commands whose failure the UR can tolerate
Capture the bytes some callers append after the UR arguments as trailing_data, and re-append them when rebuilding the calldata, so a decoded call can be rebuilt byte-for-byte
Make the chained function builders public and expose the encoder & decoder modules
Reduce CI time
Add a publish.yml GitHub Actions workflow that automatically publishes the package to PyPI and the MCP Registry with OIDC Trusted Publishing
Agent-friendly changes:
Add Encoder.function_input() / AsyncEncoder.function_input() to rebuild the calldata from a decoded call
Add decoded_input_to_dict() and transaction_to_dict() to render the decoder output as JSON-friendly dicts
Add the ur-decode and ur-encode command line tools, including ur-encode v3-path and its encode_v3_path MCP counterpart
Add the ur-mcp MCP server (optional mcp extra) so AI agents can drive the codec, including encode_calldata to rebuild the calldata from a decoded call
Annotate the MCP tools as read-only so a host can auto-approve them, and give them human-readable titles
The command descriptions (ur-encode list / describe and the list_commands / describe_command MCP tools) now describe the decoded call format and its ABI parameters, instead of the encoder methods
Add the MCP Registry metadata (server.json) to make the ur-mcp server discoverable
Add AGENTS.md and llms.txt for AI agents, plus a mcp PyPI keyword
Add tests/test_version_consistency.py to keep the packaging version, server.json and the README mcp-name: marker in sync

Overview and Points of Attention

The object of this library is to decode & encode transactions sent to the Uniswap Universal Router (UR) on Ethereum Mainnet, though it would work on any compatible chain where the UR is deployed. See Version Mapping below. This Python SDK is based on, and intended to be used with web3.py

The target audience is Python developers who are familiar with the Ethereum blockchain concepts and web3.py, and how DEXes work. The same codec is also available without Python, through the ur-decode / ur-encode command line tools and the optional ur-mcp MCP server (see "Command line interface" and "MCP server" below): both print JSON, so shell scripts and AI agents can drive it too.

⚠ Before using this library, ensure you are familiar with general blockchain concepts. The Python API also expects web3.py knowledge in particular.

⚠ Not all UR functions supported by this SDK are available through the CLI or MCP tools: run ur-encode list and look for the "rebuildable" flag.

List of supported Uniswap Universal Router Functions

Command Id	Universal Router Function	Underlying Action - Function	Supported
0x00 / 0	V3_SWAP_EXACT_IN		✅
0x01 / 1	V3_SWAP_EXACT_OUT		✅
0x02 / 2	PERMIT2_TRANSFER_FROM		✅
0x03 / 3	PERMIT2_PERMIT_BATCH		✅
0x04 / 4	SWEEP		✅
0x05 / 5	TRANSFER		✅
0x06 / 6	PAY_PORTION		✅
0x07 / 7	PAY_PORTION_FULL_PRECISION		✅
0x08 / 8	V2_SWAP_EXACT_IN		✅
0x09 / 9	V2_SWAP_EXACT_OUT		✅
0x0a / 10	PERMIT2_PERMIT		✅
0x0b / 11	WRAP_ETH		✅
0x0c / 12	UNWRAP_WETH		✅
0x0d / 13	PERMIT2_TRANSFER_FROM_BATCH		✅
0x0e / 14	BALANCE_CHECK_ERC20		✅
0x0f / 15	placeholder		N/A
0x10 / 16	V4_SWAP		✅
		0x06 - SWAP_EXACT_IN_SINGLE	✅
		0x07 - SWAP_EXACT_IN	✅
		0x08 - SWAP_EXACT_OUT_SINGLE	✅
		0x09 - SWAP_EXACT_OUT	✅
		0x0b - SETTLE	✅
		0x0c - SETTLE_ALL	✅
		0x0e - TAKE	✅
		0x0f - TAKE_ALL	✅
		0x10 - TAKE_PORTION	✅
0x11 / 17	V3_POSITION_MANAGER_PERMIT		✅
0x12 / 18	V3_POSITION_MANAGER_CALL		✅
0x13 / 19	V4_INITIALIZE_POOL		✅
0x14 / 20	V4_POSITION_MANAGER_CALL		✅
		0x02 - MINT_POSITION	✅
		0x0b - SETTLE	✅
		0x0d - SETTLE_PAIR	✅
		0x0e - TAKE	✅
		0x11 - TAKE_PAIR	✅
		0x12 - CLOSE_CURRENCY	✅
		0x13 - CLEAR_OR_TAKE	✅
		0x14 - SWEEP	✅
		0x15 - WRAP	✅
		0x16 - UNWRAP	✅
0x15 - 0x20	placeholders		N/A
0x21 / 33	EXECUTE_SUB_PLAN		✅
0x22 - 0x3f	placeholders		N/A
0x40 / 64	ACROSS_V4_DEPOSIT_V3		❌

All the ✅ commands can be decoded and encoded. V4_SWAP, V4_POSITION_MANAGER_CALL and EXECUTE_SUB_PLAN can also be decoded, but they cannot be rebuilt from a decoded call (see "How to rebuild the calldata from a decoded call").

Version Mapping

Here is the mapping between the Universal Router versions and the SDK ones

UR Version	UR address on Ethereum	Python SDK version
v2.1.2	`0x23617e59A5925b2A4Bf75d73ff6711cD0b29De85`	v3.1.0 & v4.0.0
v2.1.1	`0x4C82D1fBFe28C977cBB58D8C7FF8FCF9F70a2cCA`	v3.0.0
v2	`0x66a9893cC07D91D95644AEDD05D03f95e1dBA8Af`	v2.0.0 & v2.1.0
v1.2	`0x3fC91A3afd70395Cd496C647d5a6CC9D4B2b7FAD`	v0.9.0 to v1.2.1
v1	`0xEf1c6E67703c7BD7107eed8303Fbe6EC2554BF6B`	v0.8.0

Installation

A good practice is to use Python virtual environments, here is a tutorial.

The library can be pip installed from pypi.org as usual:

# update pip to latest version if needed

pip install -U pip

install the decoder from pypi.org

pip install uniswap-universal-router-decoder

To install it from source:

pip install .

or for contributors:

pip install -e '.[mc

Only the beginning is shown; read the rest in the repo

Uniswap Universal Router Decoder

Overview

PopNx MCP’s three pillars

What you can do with it

Install

Before you install

Values you fill in

What it can do

Basic checksi

Maker matches the repo

Still maintained

Has a licence

Endpoint responds

Sign-in with OAuth

No hidden instructions in tool descriptions

Compared with others in Otheri

Common questions

Alternatives

Spec Driven Development

Remote Desktop Commander

SwarmMemo

README from the maker

Uniswap Universal Router Decoder & Encoder

Project Information

Code Quality

Release Notes

v4.0.0 - breaking changes

Overview and Points of Attention

List of supported Uniswap Universal Router Functions

Version Mapping

Installation

install the decoder from pypi.org