Guides
Build with APIStack
Practical tutorials with code you can copy. Every example was tested against production, and the responses shown are real.
Connect APIStack to your AI stack
Recipes for agent frameworks and coding assistants. Each one was run against the live MCP server.
Give a Vercel AI SDK app 100+ tools with MCP
Connect the APIStack MCP server to the Vercel AI SDK with createMCPClient and let generateText or streamText search and call 100+ APIs.
Use APIStack tools in the OpenAI Agents SDK (Python and TypeScript)
Connect the APIStack MCP server to an OpenAI Agents SDK agent in Python or TypeScript with MCPServerStreamableHttp: calculators, validators, web and data tools.
Call APIStack from the OpenAI Responses API with a remote MCP tool
Let OpenAI call APIStack for you: add the MCP server as a tool in a Responses API request, with no agent framework and no tool-calling loop in your code.
Load APIStack tools into a LangChain or LangGraph agent
Use langchain-mcp-adapters to load APIStack's MCP tools into a LangChain v1 agent (create_agent) or a LangGraph graph over Streamable HTTP.
Add APIStack to Claude Code, Claude Desktop, Cursor and VS Code
Copy-paste MCP configuration for Claude Code, Claude Desktop, Cursor and VS Code so your coding assistant can call 100+ APIStack tools.
Solve a specific problem
Real requests with the real responses they return, in cURL, JavaScript and Python.
Validate email addresses at sign-up (and catch typos like gmial.com)
Check an email address before you store it: syntax, MX records, disposable domains, role accounts and typo suggestions, with one API call in cURL, JavaScript or Python.
Count business days between two dates, excluding public holidays
Count working days between two dates or add N business days to a date, skipping weekends and US, UK, Canadian, Australian, German, French or Japanese public holidays.
Validate international phone numbers and detect the line type
Validate a phone number in E.164 format, find its country, and tell mobile from landline before you send an SMS, with one GET request.
Check SSL certificate expiry for any domain
Get a domain's TLS certificate details (issuer, validity dates, days until expiry, SANs and chain) with one API call, and alert before it expires.
Calculate loan payments and total interest (without letting an LLM do the math)
Get the monthly payment, total interest and first/last payment split for any loan amount, rate and term with one GET request. Useful for fintech apps and AI assistants.
Convert HTML to clean Markdown for LLM prompts and RAG
Turn HTML into clean Markdown (headings, links, lists and tables preserved) to cut prompt tokens and improve retrieval quality, with one POST request.
Add months to a date correctly (Jan 31 + 1 month = Feb 28)
Add or subtract days, weeks, months or years from a date with end-of-month handling: Jan 31 + 1 month is Feb 28, not March 3. One API call, plus day of week, quarter and week number.
Calculate a full mortgage payment: principal, interest, taxes and insurance
Get the full monthly mortgage payment (principal and interest, property tax, insurance, HOA and PMI) plus total interest for any home price, down payment, rate and term, with one POST request.
Look up DNS records for a domain (A, MX, TXT, NS) with one API call
Fetch a domain's DNS records (A, AAAA, MX, TXT, NS) as JSON with one GET request: check email routing, SPF records and domain verification without running dig.
Find the university behind an email address (student and academic verification)
Turn an email address or domain into the university it belongs to (name, country, website) across 10,000+ universities in 200 countries. Useful for student discounts, academic sign-ups and lead enrichment.
Get the largest cities in any country, or the cities near a location
List a country's largest cities by population, or find cities within a radius of any coordinates, with coordinates, state/province, population and time zone. 32,000+ cities in 245 countries from GeoNames.