Add Congress.gov MCP server

[AshwinSundar]

Description

This PR adds an MCP server to retrieve real-time information about United States Congerss proceedings, via the official Congress.gov API.

Features

• Can retrieve and utilize information from any bill that has entered the U.S. Congress since 1873. A smaller subset of bills from between 1799-1873 is also available.
• Augment LLM capabilities with a wide variety of other U.S. Congress artifacts, such as resolutions, congressional voting results, communications, roll call votes, nominations, and more (full list available here -> https://api.congress.gov/#/)

Example Prompts

• What did my U.S. Senators from Colorado do this week?

• What is the scope of H.R. 1, a.k.a. the "Big Beatiful Bill"?

Server Details

• Server: filesystem (installation instructions provided in README.md)
• Changes to: N/A

Motivation and Context

It is challenging to learn about the real-time proceedings of the U.S. Congress, and place these proceedings in context with the full history of Congress. This MCP server enables a local instance of Claude Desktop, Claude Code, and other clients to programmatically retrieve data from the Congress.gov API and augment it's knowledge and answer. This provides users a way to explore the actions of U.S. Congress on their own terms, and provides an alternate to mass media consumption and biases.

How Has This Been Tested?

Via Claude Code, Claude Desktop, and unit tests on each endpoint.

Breaking Changes

N/A

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Protocol Documentation
• My changes follows MCP security best practices
• I have updated the server's README accordingly
• I have tested this with an LLM client
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have documented all environment variables and configuration options

Additional context