LastSearch

lastsearch

Reliable research infrastructure for AI agents. The research layer your agents are missing.

MCP server with real-time web search, evidence extraction, and structured citations. Drop into Claude Desktop, Cursor, Windsurf, LangChain, CrewAI, or any agent pipeline.

What it does

Instead of letting your AI hallucinate, lastsearch gives it real-time access to the web with structured, cited answers:

Your question → Web search → Neural rerank → Fetch pages → Extract claims → Verify → Cited answer (streamed)

Every answer includes:

• Claims with source URLs, verification status, and consensus level
• Evidence-based confidence score (0-1), not LLM self-assessed, auto-calibrated from feedback
• Source quotes verified against actual page text
• Atomic claim decomposition — compound facts split and verified independently
• Execution trace with timing
• 3 depth modes — "fast" (default), "thorough" (auto-retry with rephrased queries), "deep" (premium multi-step agentic research: iterative think-search-extract-evaluate cycles with gap analysis, up to 4 steps, targets 0.85 confidence — requires LastSearch key + sign-in, 3x quota cost, falls back to thorough when exhausted)

Premium Features (with LASTSEARCH_API_KEY)

Users with a LastSearch API key (ls_xxx) get enhanced verification:

• Semantic re-ranking — search results re-scored by semantic query-document relevance
• Semantic reranking — evidence matched by meaning, not just keywords
• Multi-provider search — parallel search across multiple sources for broader coverage
• Multi-pass consistency — claims cross-checked across independent extraction passes
• Deep reasoning mode — multi-step agentic research with iterative think-search-extract-evaluate cycles, gap analysis, and cross-step claim merging (up to 4 steps, 3x quota cost, 100 deep queries/day)
• Research Sessions — persistent memory across queries

Free LastSearch key users get a generous daily quota (100 premium queries/day, or ~33 deep queries/day at 3x cost each). When exceeded, queries gracefully fall back to keyword verification (deep falls back to thorough). Quota resets every 24 hours.

Sign up at lastsearch.ai for a free API key — 100 premium queries/day with full verification pipeline.

Quick Start

npx lastsearch setup

This auto-configures Claude Desktop. You'll need a LastSearch API key — get one free at lastsearch.ai/dashboard.

Manual Setup

Claude Desktop

Add to ~/Library/Application Support/Claude/claude_desktop_config.json:

{

"mcpServers": { "lastsearch": { "command": "npx", "args": ["-y", "lastsearch@1.4.3"], "env": { "LASTSEARCH_API_KEY": "ls_xxx" } } } }

Cursor / Windsurf

Add to your MCP settings:

{

"lastsearch": { "command": "npx", "args": ["-y", "lastsearch@1.4.3"], "env": { "LASTSEARCH_API_KEY": "ls_xxx" } } }

HTTP Transport

Run as an HTTP server for browser-based clients, Smithery, or any HTTP-capable agent:

# Start with HTTP transport (listens on 127.0.0.1 only)

npx lastsearch --http

Or set the port via environment variable

MCP_HTTP_PORT=3100 npx lastsearch --http

Every request needs a bearer token. By default a random token is generated at each launch and printed once to stderr; set LASTSEARCH_HTTP_TOKEN (16+ characters) to use your own:

export LASTSEARCH_HTTP_TOKEN="$(openssl rand -base64 32)"

npx lastsearch --http

curl -H "Authorization: Bearer $LASTSEARCH_HTTP_TOKEN" http://127.0.0.1:3100/health

The server exposes:

• POST /mcp — MCP Streamable HTTP endpoint
• GET /health — Health check

By default the server only accepts requests addressed to 127.0.0.1, localhost or ::1, and refuses requests from browser pages on other origins. To listen on another interface, pass --host explicitly (a warning is printed); the token is still required. Request bodies are limited to 1 MB.

Docker

Inside a container the server must listen on 0.0.0.0, so pass --host 0.0.0.0 explicitly, set a token, and publish the port on the host's loopback interface only:

docker build -t lastsearch ./apps/mcp

docker run -p 127.0.0.1:3100:3100 \ -e LASTSEARCH_API_KEY=ls_xxx \ -e LASTSEARCH_HTTP_TOKEN="$(openssl rand -base64 32)" \ lastsearch --host 0.0.0.0

Clients send Authorization: Bearer with every request.

MCP Tools

Note: All tools require a LastSearch API key (ls_xxx). Get a free one at lastsearch.ai/dashboard.

Examples

Quick lookup:

*"Use answer to explain what causes aurora borealis"*

Higher accuracy:

*"Use answer with depth thorough to research quantum computing"*

Deep research (multi-step, requires LastSearch key):

*"Use answer with depth deep to compare CRISPR approaches for sickle cell disease"*

Deep mode runs iterative think-search-extract-evaluate cycles: gap analysis identifies missing info, follow-up queries fill the gaps, and claims/sources are merged across steps with final re-verification. Targets 0.85 confidence across up to 4 steps. Falls back to thorough without a LastSearch key or when quota is exhausted.

Contradiction detection:

*"Use answer with depth thorough to check if coffee is good for health, and show me any contradictions"*

Research session:

*"Create a session called quantum-research, then ask about quantum entanglement, then ask how entanglement is used in computing"*

Enterprise search:

*"Use answer to search our Elasticsearch at https://es.company.com/kb/_search for our refund policy"*

Response structure

{

"answer": "Aurora borealis occurs when charged particles from the Sun...", "confidence": 0.92, "claims": [ { "claim": "Aurora borealis is caused by solar wind particles...", "sources": ["https://en.wikipedia.org/wiki/Aurora"], "verified": true, "verificationScore": 0.82, "consensusLevel": "strong" } ], "sources": [ { "url": "https://en.wikipedia.org/wiki/Aurora", "title": "Aurora - Wikipedia", "domain": "en.wikipedia.org", "quote": "An aurora is a natural light display...", "verified": true, "authority": 0.70 } ], "contradictions": [], "reasoningSteps": [] }

Why lastsearch?

Reliability

All API calls include automatic retry with exponential backoff on transient failures (429 rate limits, 5xx server errors). Auth errors fail immediately — no wasted retries.

Tech Stack

• Search: Multi-provider (parallel search across sources)
• Parsing: @mozilla/readability + linkedom
• AI: OpenRouter (100+ models)
• Verification: Hybrid keyword and semantic verification
• Protocol: Model Context Protocol (MCP)

Agent Skills

Pre-built skills that teach coding agents when to use LastSearch tools:

npx skills add lastsearch-hq/lastsearch-skills

Skills work with Claude Code, Codex CLI, Gemini CLI, Cursor, and more. View skills →

Community

• Discord
• GitHub

License

Apache 2.0

Data, privacy and terms

This package sends your requests (queries, URLs and documents you ask it to verify) and your LastSearch API key to the hosted LastSearch API at lastsearch.ai. Queries and results are stored there and used, in aggregate and without identifiers, to improve verification, as described in the Privacy Policy. The package itself collects no telemetry. Use of the hosted API is subject to the Terms.

LastSearch is a free, non-commercial passion project run by an individual developer. Answers, citations and confidence scores are AI-generated research, not professional advice; verify anything important against primary sources.