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Thomson Reuters Westlaw MCP Server

Official Thomson Reuters MCP connector that brings Westlaw Deep Research, KeyCite signals, and Practical Law citations into Claude.

Legal by Thomson Reuters OAuth2 active
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Overview

The Thomson Reuters CoCounsel Legal MCP connector exposes Westlaw Deep Research to Claude through the Model Context Protocol. Announced as part of the May 2026 Thomson Reuters and Anthropic partnership expansion, it lets legal professionals run agentic research that returns fully cited reports grounded in case law, statutes, regulations, secondary sources, and Practical Law commentary, with citations validated against KeyCite. Thomson Reuters describes the underlying corpus as 1.9 billion Westlaw and Practical Law documents plus 1.4 billion KeyCite validity signals.

The connector is hosted by Thomson Reuters and authenticated through OAuth against an existing Thomson Reuters identity. It is exposed in two ways: as a native Claude Desktop connector that is installed from Settings then Connectors, and as the partner plugin cocounsel-legal@claude-for-legal distributed through the open-source anthropics/claude-for-legal marketplace for use in Claude Code and Claude Cowork. Both surfaces talk to the same remote MCP endpoint at legal-mcp.thomsonreuters.com.

The tool surface is intentionally narrow and focused on long-running research jobs rather than ad hoc lookups. A research run is started, polled, and then returned as a cited report, and follow up questions can be appended to the same research conversation. Thomson Reuters scopes the connector to research questions that can be answered through caselaw, statutes, regulations, and administrative materials. It is not intended for full document retrieval, drafting, outcome prediction, foreign law, or Boolean searching.

Tools

Tool Description
start_deep_research Initiates a jurisdiction-aware Westlaw Deep Research run across US federal and state law, covering case law, statutes, regulations, secondary sources, and Practical Law.
check_deep_research_status Polls the status of an in-progress Deep Research job.
get_deep_research_report Retrieves the completed cited research report with inline, linked citations to Westlaw and Practical Law sources.
follow_up_deep_research Continues analysis on an existing research conversation without restarting from scratch.
Setup Guide

Prerequisites

  • Active Thomson Reuters account with a CoCounsel Legal subscription
  • The MCP connector enabled on the account (contact cocounselsupport@tr.com if it is not)
  • Claude Desktop, Claude Code, or Claude Cowork

Option A: Claude Desktop connector (recommended)

  1. Open Claude Desktop and sign in to your Claude account.
  2. Go to Settings, then Connectors.
  3. Search for "CoCounsel Legal" and click Connect.
  4. Complete the Thomson Reuters sign-in flow when the authorization window appears.
  5. The connector becomes available in the conversation tools menu. Authentication only needs to be completed once.

Option B: Claude Code / Cowork plugin

The partner plugin ships through the claude-for-legal marketplace maintained by Anthropic.

/plugin install cocounsel-legal@claude-for-legal

After install, invoke the research workflow with:

/cocounsel-legal:deep-research

OAuth still runs against Thomson Reuters on first use. The plugin source lives under external_plugins/cocounsel-legal/ in the anthropics/claude-for-legal repository.

Support

Entitlement, access, and connector issues go to cocounselsupport@tr.com.

Use Cases
  • Run a multi-jurisdiction Westlaw Deep Research memo on an emerging legal question and receive a citation-linked report inside Claude.
  • Validate authority for a draft argument by triggering Deep Research against case law, statutes, and KeyCite signals.
  • Pull a Practical Law grounded research report on a transactional topic such as restrictive covenants or data processing addenda.
  • Continue an earlier research conversation with targeted follow up questions instead of starting a new query.
  • Compare how courts in up to three US jurisdictions have ruled on the same doctrinal issue in a single research run.
Example Prompts
  • "Use CoCounsel Legal to run Westlaw Deep Research on whether non-compete agreements are enforceable against remote employees in California, New York, and Texas."
  • "Start a Deep Research report on recent Delaware Chancery rulings interpreting MAE clauses in M&A agreements, then summarize the cited authority."
  • "Check the status of my running Westlaw Deep Research job and return the report when it is ready."
  • "Follow up on the FTC Section 5 unfair practices research conversation: how have circuit courts treated the new rulemaking authority post 2024?"
  • "Pull Practical Law and Westlaw authority on the IRS economic substance doctrine and return a cited memo."
Pros
  • Official, vendor-built and vendor-hosted connector from Thomson Reuters, no self-hosting or scraping required.
  • Returns fully cited reports linked back to Westlaw and Practical Law with KeyCite validity signals.
  • OAuth-based install through Claude Desktop Connectors is a one-time flow, and a parallel cocounsel-legal plugin is available for Claude Code and Cowork.
  • Fiduciary-grade data handling: Thomson Reuters states customer data is not used to train third-party models.
Limitations
  • Requires a paid CoCounsel Legal subscription with the MCP connector explicitly enabled on the account.
  • Narrow tool surface focused on Deep Research; it is not designed for full document retrieval, drafting, outcome prediction, foreign law, or Boolean searches.
  • Limited to up to three US jurisdictions per research run.
Alternatives
  • Free Law Project / CourtListener MCP for open access US case law and dockets.
  • LexisNexis Protégé and other vendor legal research assistants as a commercial alternative to Westlaw research.
  • Community legal MCP servers such as agentic-ops/legal-mcp that aggregate public legal sources, though without Westlaw or KeyCite content.
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