MCP & ChatGPT apps guide
MCP vs API: what SaaS teams actually need
Updated 2026-10-26
Short answer: Your API is for developers writing code. An MCP server is for AI assistants acting for a user. You keep the API and add MCP as a thin, curated layer on top of it.
The difference in one table
- Consumer: API = a developer's code; MCP = an AI client like Claude or ChatGPT.
- Discovery: API = docs a human reads; MCP = the client lists tools and schemas at runtime.
- Granularity: API = every endpoint; MCP = a few task-shaped tools.
- Auth: API = keys or OAuth for apps; MCP = OAuth 2.1 per end user for remote servers.
- Output: API = full objects; MCP = trimmed text or JSON a model can reason over.
When MCP is worth building
- Customers already paste your data into ChatGPT or Claude.
- Competitors list a connector and you get asked about it in sales.
- You have a public API and a technical audience.
When it is not yet
- No public API and no plan for one.
- Your data is too sensitive to expose without a security review you have not done.
MCP vs function calling
Function calling is how one app wires tools into one model. MCP is a standard so any compatible client can use your tools without you shipping an integration for each one.
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Agencies in our index that mention MCP work
Listed in their normal directory order. Our own build service is not part of this list or the rankings.
- Teamvoy (Ukraine)
- AiAdvisors (Poland)
- Context Studios (Germany)
- AI Agency Manchester (United Kingdom)
- Focused (United States)
- Autor Technologies (Canada)
- Pentridge (United States)
- Hourglass AI (Australia)
- Enabled Minds (United States)
- AppStream Studio (United States)
Questions
Does MCP replace REST?
No. Most MCP servers call the product's REST or GraphQL API underneath.
Is MCP only for Claude?
No. It is an open protocol supported by Claude, ChatGPT, and many IDEs and agent frameworks.
Can I expose my whole API as MCP?
You can, but curated tools work much better.
More MCP guides
- How to build an MCP server for your SaaS product
- How to add a ChatGPT app to your SaaS
- MCP server development cost: what SaaS teams pay (estimates)
- MCP server authentication: an OAuth 2.1 guide for SaaS teams
- MCP server for a REST API: generate from OpenAPI or hand-write?
- MCP server security and rate limiting checklist
- How to publish an MCP server: official registry, Smithery and awesome lists
- MCP server for CRM SaaS: tools, risks and scope
- MCP server for billing and subscription SaaS
- MCP server for scheduling and booking SaaS
- MCP server for healthcare SaaS: what is safe to build first
- MCP server for helpdesk and support SaaS
- Open-source example: Canny MCP server
Cost and effort figures on this page are rough estimates, not quotes.