Groundtruth

Current, official documentation for coding agents, fetched when they ask.

GroundTruth is a self-hosted MCP server and command-line tool. Models write code from what they were trained on, so they still wrap components in forwardRef after React 19 made ref a regular prop, call cookies() synchronously after Next.js made it async, and emit @tailwind directives that Tailwind v4 replaced with @import "tailwindcss". GroundTruth gives the agent the library's own documentation at request time: it reads llms.txt, the docs site as markdown, or the GitHub repository, ranks the sections that answer the question, and checks that the answer covers the topic before returning it. It also audits your source with 107+ patterns and links every finding to the current fix. It runs on your machine. No account, no API key, no rate limit of its own.

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Install (60 seconds)

Requires Node.js 24 or newer.

Claude Code

claude mcp add gt -- npx -y @groundtruth-mcp/gt-mcp@latest

Cursor, Claude Desktop, Windsurf and other clients that use an mcpServers block (.cursor/mcp.json, claude_desktop_config.json, ~/.codeium/windsurf/mcp_config.json):

{

"mcpServers": { "gt": { "command": "npx", "args": ["-y", "@groundtruth-mcp/gt-mcp@latest"] } } }

VS Code (.vscode/mcp.json):

{

"servers": { "gt": { "type": "stdio", "command": "npx", "args": ["-y", "@groundtruth-mcp/gt-mcp@latest"] } } }

Any other MCP client: run npx -y @groundtruth-mcp/gt-mcp@latest as a stdio server.

Command line (same tools, no MCP client needed):

npm install -g @groundtruth-mcp/gt-mcp

gt-mcp bp nextjs caching

@latest makes npx pick up new releases on the next session start. When a newer version exists, tool responses carry a one-line notice (GT_NO_UPDATE_CHECK=1 turns the check off).

Optional: GitHub token

GroundTruth reads READMEs, release notes, migration guides and code examples from GitHub. Without a token GitHub allows 60 requests per hour. A token with no extra scopes raises that to 5,000 and enables code search in gt_examples.

claude mcp add gt -e GT_GITHUB_TOKEN=ghp_yourtoken -- npx -y @groundtruth-mcp/gt-mcp@latest

In a JSON config, add "env": { "GT_GITHUB_TOKEN": "ghp_yourtoken" } next to args.

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What you get

Fourteen tools. Each does one job, and each is also a CLI command.

The server also exposes 2 MCP resources (library-registry, library-docs) and 8 prompts (audit-my-project, upgrade-check, best-practices-scan, compare-libraries, security-check, migration-guide, find-examples, dependency-audit).

You don't need the tool names. Ask in plain language:

use gt for nextjs

use gt for drizzle migrations gt audit use gt to check WCAG focus indicators use gt for OpenTelemetry setup find all issues and fix with gt

Or call tools directly:

gt_resolve_library({ libraryName: "nestjs" })

gt_get_docs({ libraryId: "nestjs/nest", topic: "guards" }) gt_best_practices({ libraryId: "vercel/next.js", topic: "caching" }) gt_auto_scan({ projectPath: "." }) gt_search({ query: "OWASP SQL injection prevention" }) gt_audit({ projectPath: ".", categories: ["security", "accessibility"] }) gt_changelog({ libraryId: "vercel/next.js", version: "15" }) gt_compat({ feature: "CSS container queries", environments: ["safari"] }) gt_compare({ libraries: ["prisma", "drizzle-orm"], criteria: "TypeScript support" }) gt_examples({ library: "hono", pattern: "middleware" })

gt_audit

Walks your project, runs 107+ patterns across 18 categories, reports each issue at file:line, then fetches the fix from the authoritative source.

gt_audit({ categories: ["all"] })                      // all 18 categories

gt_audit({ categories: ["security", "node"] }) // OWASP + Node.js gt_audit({ categories: ["python", "security"] }) // Python OWASP scan gt_audit({ categories: ["accessibility"] }) // WCAG AA gt_audit({ categories: ["typescript", "react"] }) // type safety + React rules

Sample output:

## [CRITICAL] SQL built via template literal

Category: security | Severity: critical | Count: 2

Fix: db.query('SELECT * FROM users WHERE id = $1', [userId])

Files:

• src/db/users.ts:47
• src/api/search.ts:23

Live fix: OWASP SQL Injection Prevention Cheat Sheet

gt_auto_scan

Point it at a project root. It reads the manifest and lockfile, works out which libraries you use and at which versions, and returns best practices for each, top libraries first. Default output is about 15K characters.

Reads package.json, deno.json, requirements.txt, pyproject.toml, Cargo.toml, go.mod, pom.xml, build.gradle, build.gradle.kts, composer.json, Gemfile and pubspec.yaml.

gt_search

For anything that isn't one library.

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CLI

gt-mcp runs the same 14 tools in-process and prints the answer. With no arguments, gt-mcp is the stdio MCP server, exactly as before.

gt-mcp docs react useEffect                  # live docs for one topic

gt-mcp bp nextjs caching # best practices gt-mcp search "OWASP SSRF prevention" gt-mcp audit . # audit the current project gt-mcp scan . # best practices for every dependency gt-mcp compat "CSS container queries" gt-mcp ask "how do I paginate with drizzle" # let gt_dispatch pick the tool gt-mcp call gt_compare '{"libraries":["prisma","drizzle-orm"]}' echo '{"libraryName":"drizzle"}' | gt-mcp call gt_resolve_library -

Exit codes: 0 ok, 1 tool error, 2 usage error. Logs stay quiet on stderr unless something goes wrong (GT_LOG_LEVEL defaults to warn for commands). The server flags still work: --version, --health, --routing-table, --help.

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Performance

Measured on one machine with the same harness, published 7.5.0 against 8.0.0. Network timings depend on your connection and on the docs site.

Fewer tokens per session and per answer:

| gt_auto_scan default o