Arc & Ledger Tax Tools - MCP server

A public, no-auth remote MCP server that exposes Arc & Ledger's free tax calculators and intake funnel as tools inside AI assistants (Claude, ChatGPT). Runs as a stateless Cloudflare Worker; nothing is filed, purchased, or stored.

• Endpoint: https://mcp.arcandledger.com/mcp (Streamable HTTP)
• Docs: https://www.arcandledger.com/mcp
• Privacy: https://www.arcandledger.com/mcp/privacy

Tools

Tool	Purpose
decode_irs_notice	Explain an IRS notice, its deadline, and what to do.
check_fbar_fatca	FBAR / Form 8938 obligations, thresholds, catch-up.
compare_llc_scorp	SE tax vs salary+distribution, CA franchise, break-even.
estimate_quarterly_taxes	Federal + CA quarterly estimates with safe harbor.
estimate_rental_income	Net rental income, depreciation, passive-loss allowance, 14-day rule.
deadline_calendar	US filing deadlines + penalties for founders (1120/5472, 1040-NR, FBAR, BOI).
check_itin_eligibility	ITIN eligibility, W-7 category, documents; Enrolled Agent prepares the W-7 and represents you.
estimate_irs_penalty	Failure-to-file / failure-to-pay penalties + interest on a balance; abatement.
compare_formation_states	Wyoming vs New Mexico vs Delaware vs California for a US LLC.
check_sales_tax_nexus	Economic + physical (FBA) sales-tax nexus by state.
get_fee_quote	Published fee range and line items for firm services.
book_consultation	First-party booking link + office identity.

Plus five prompts (three English, two Turkish for founders): decode_my_irs_notice, am_i_required_to_file_fbar, should_i_be_an_scorp, abd_sirket_vergi_takvimi, itin_almali_miyim.

And four read-only resources (arcledger://office, arcledger://services, arcledger://fee-catalog, arcledger://tool-directory) so an assistant can cite the firm's identity, service directory, and fee catalog directly.

Design

• Stateless Streamable-HTTP JSON-RPC handler (no sessions, no Durable Objects). Uses the official @modelcontextprotocol/sdk types + zod.
• No hardcoded prices or rates. src/pricing.ts re-exports the website's src/data/pricing.ts; src/rates.ts re-exports src/config/taxConstants2026.ts and adds only genuinely-new pieces (safe harbor, CA S-corp rate, Form 8938 matrix, CA 30/40/0/30). Both are the single sources of truth.
• Shared response envelope: every tool returns the same disclaimer, a first-party source_url, and one first-party next_step handoff.
• Privacy: inputs processed in memory; logs carry only tool name, timestamp, and coarse enums (never free text or dollar amounts). 30-day retention.
• Rate limiting: per-IP token bucket (60/min, burst 10) + the native RATE_LIMITER binding when bound.

Commands

npm install
npm test              # 47 tests: protocol, HTTP surface, tool correctness, drift guard
npm run typecheck
npm run dev           # wrangler dev (local)
npm run deploy        # wrangler deploy (needs the Cloudflare account)
npm run gen:products  # regenerate ../public/feeds/products.json from pricing.ts
node scripts/gen-examples.mjs      # regenerate docs/worked-examples.json

Layout

src/
  index.ts            Worker entry: /mcp, /healthz, /version, CORS, rate limit
  registry.ts         The 6 tools + 3 prompts
  pricing.ts          Adapter -> website pricing.ts (SSOT for prices)
  rates.ts            Adapter -> taxConstants2026.ts + server-only tax constants
  lib/                mcp (protocol), response, logging, rateLimit, tax, dates, schemas
  tools/              one file per tool
  data/notices.ts     IRS notice registry
submissions/          Anthropic + OpenAI payloads + listing copy
assets/               logo, favicon, response screenshots + paired prompts