tessera-mcp-server

The MCP server that returns money, not data.

Status: v0.1.3 — published 2026-05-27 on npm with sigstore SLSA provenance v1, listed on registry.modelcontextprotocol.io.

Tessera is an LLM proxy that optimizes API spend through multi-provider routing, prompt compression, audit-immutable logging, output-length prediction, and batch arbitrage. This package exposes Tessera as an MCP server for tool-using agents — Claude Desktop, Claude Code, Cursor, Cline, Continue, Goose, Zed.

Where other LLM-infrastructure MCP servers return logs, traces, or prompt metadata, this one returns savings decisions: what's drifting, what to switch, what to approve, what to audit.

See it in action

▶ 41-second walkthrough: live counter ticks · baseline $74,800 → actual $30,000 ($44,800 saved, 60% reduction) · audit-immutable savings ledger. Click to play.

Install

npx @tessera-llm/mcp-server

Or add to your client config:

Claude Desktop (~/Library/Application Support/Claude/claude_desktop_config.json on macOS, %APPDATA%\Claude\claude_desktop_config.json on Windows):

{
  "mcpServers": {
    "tessera": {
      "command": "npx",
      "args": ["-y", "@tessera-llm/mcp-server"],
      "env": {
        "TESSERA_API_KEY": "tk_..."
      }
    }
  }
}

Claude Code (.mcp.json in project root):

{
  "mcpServers": {
    "tessera": {
      "command": "npx",
      "args": ["-y", "@tessera-llm/mcp-server"],
      "env": {
        "TESSERA_API_KEY": "tk_..."
      }
    }
  }
}

Cursor (~/.cursor/mcp.json):

{
  "mcpServers": {
    "tessera": {
      "command": "npx",
      "args": ["-y", "@tessera-llm/mcp-server"],
      "env": { "TESSERA_API_KEY": "tk_..." }
    }
  }
}

Get a TESSERA_API_KEY at tesseraai.io/dev — Free Sandbox is 60M tokens/month with no card.

Tools

v0.1 exposes 6 tools (5 read + 1 mutate). Hard cap — no tool sprawl.

Provider config writes, API-key management, composition cap changes, and Stripe operations are deliberately NOT in this surface — they live in the dashboard, where blast-radius requires explicit modal confirmation.

Transport

• stdio (default) — local clients (Claude Desktop, Cursor, Cline, Continue, Claude Code)
• Streamable HTTP (optional) — set TESSERA_MCP_TRANSPORT=http to bind on localhost:8788 for remote / Goose / Zed-via-mcp-remote

SSE (deprecated in MCP spec 2025-11-25) is not supported.

Auth

TESSERA_API_KEY env var or Authorization: Bearer <key> header (HTTP transport). Same API key as the SDK — tk_* format. Future v0.2: OAuth 2.1 (aligned with MCP spec RC 2026-07-28).

Security posture

• Tools receiving user-controlled content (ledger notes, recommendation rationale strings, workload names) are labelled __untrusted__ to prevent prompt-injection cascade per the Supabase/Cursor 2025 pattern.
• mcp-scan (Invariant Labs) runs in CI to catch tool-poisoning attacks in tool descriptions.
• No execute_code escape hatch. Typed verbs only.
• No session-based auth. Every request authenticates independently per MCP spec 2026 requirement.

License

Apache-2.0. Tessera is a product of Fintechagency OÜ (Estonia, Tallinn).

Links

• Tessera landing: tesseraai.io
• Free Sandbox signup: tesseraai.io/dev
• How it works: tesseraai.io/how-it-works
• MCP protocol spec: modelcontextprotocol.io