Generate your MCP server, or have a custom Claude connector built?
Generate your MCP server from your OpenAPI spec when the API is clean, your engineers will own the server, and broad coverage matters most: Speakeasy writes a TypeScript server, Stainless ships one inside its TypeScript SDK, Zuplo serves one from your API gateway, and FastMCP converts a spec in one call. Have a custom connector built when it should be designed around the jobs your customers do, held to directory review, and shipped without pulling engineers off the roadmap. FastMCP's own docs say "LLMs achieve significantly better performance with well-designed and curated MCP servers than with auto-converted OpenAPI servers," and Anthropic's directory requires a title and a readOnlyHint or destructiveHint on every tool. We, Modern Mustard Seed, build the second kind: Nine of our own connectors are listed in Anthropic's Claude directory.
Last checked October 26, 2026. Competitor facts are from their own pages, linked below.
Further reading: The best MCP server and Claude connector developers, How to get listed in the Claude directory
Generated a server already?
Send it over. We will tell you what directory review will ask about it.
Book a Discovery CallAn MCP generator or platform (Speakeasy, Stainless, FastMCP, Zuplo, Cloudflare, APIMatic, Postman, Mintlify) vs A custom connector built by Modern Mustard Seed
| Factor | An MCP generator or platform (Speakeasy, Stainless, FastMCP, Zuplo, Cloudflare, APIMatic, Postman, Mintlify) | A custom connector built by Modern Mustard Seed |
|---|---|---|
| What you get | Tools generated from your API: Speakeasy writes a TypeScript server from your OpenAPI document, Stainless ships a code-mode server inside your TypeScript SDK, Zuplo derives tools from operations you mark, Postman makes one tool per request, and Mintlify generates a docs search server. Cloudflare gives you hosting and an OAuth library; you write the tools. | Tools designed around the jobs your customers come to you for, each mapped to a real endpoint, with read tools split from write tools. |
| OAuth | Varies: Speakeasy offers an OAuth proxy set up with its team, Stainless can generate a Cloudflare Worker that acts as the OAuth server, Zuplo needs your own authorization server, and APIMatic lists client credentials and password flows. | OAuth sign-in built for your API, so each customer connects their own account and sees only their own data. |
| Who maintains it | Your engineers. Stainless regenerates when your spec changes, and FastMCP Gateway redeploys on every push. | We do, under Connector Care, or your team takes it over; the code is in your repository either way. |
| Directory review | Not covered on the pages we read: none of the generator pages describes help with Anthropic's directory submission. | We prepare the docs, privacy page, test account and annotations, and submit to Anthropic's Claude directory and to ChatGPT. The listing decision is theirs. |
| Maturity, by their own words | Stainless calls MCP generation experimental, APIMatic's generator is in alpha, and FastMCP recommends its converter for prototyping. | Nine of our own connectors are listed in Anthropic's Claude directory, and 15 servers are published in the official MCP Registry. |
| Price | Published on October 26, 2026: Stainless Free for up to 5 generators; FastMCP free and open source, its Gateway Developer plan $35 per developer a month plus usage; Zuplo Builder $25 a month; Mintlify Pro $450 a month billed annually; Cloudflare Workers Paid from a $5 monthly minimum. Speakeasy and APIMatic show no public price for MCP generation. | Set package price, quoted after a free discovery call |
What you get
An MCP generator or platform (Speakeasy, Stainless, FastMCP, Zuplo, Cloudflare, APIMatic, Postman, Mintlify)
Tools generated from your API: Speakeasy writes a TypeScript server from your OpenAPI document, Stainless ships a code-mode server inside your TypeScript SDK, Zuplo derives tools from operations you mark, Postman makes one tool per request, and Mintlify generates a docs search server. Cloudflare gives you hosting and an OAuth library; you write the tools.
A custom connector built by Modern Mustard Seed
Tools designed around the jobs your customers come to you for, each mapped to a real endpoint, with read tools split from write tools.
OAuth
An MCP generator or platform (Speakeasy, Stainless, FastMCP, Zuplo, Cloudflare, APIMatic, Postman, Mintlify)
Varies: Speakeasy offers an OAuth proxy set up with its team, Stainless can generate a Cloudflare Worker that acts as the OAuth server, Zuplo needs your own authorization server, and APIMatic lists client credentials and password flows.
A custom connector built by Modern Mustard Seed
OAuth sign-in built for your API, so each customer connects their own account and sees only their own data.
Who maintains it
An MCP generator or platform (Speakeasy, Stainless, FastMCP, Zuplo, Cloudflare, APIMatic, Postman, Mintlify)
Your engineers. Stainless regenerates when your spec changes, and FastMCP Gateway redeploys on every push.
A custom connector built by Modern Mustard Seed
We do, under Connector Care, or your team takes it over; the code is in your repository either way.
Directory review
An MCP generator or platform (Speakeasy, Stainless, FastMCP, Zuplo, Cloudflare, APIMatic, Postman, Mintlify)
Not covered on the pages we read: none of the generator pages describes help with Anthropic's directory submission.
A custom connector built by Modern Mustard Seed
We prepare the docs, privacy page, test account and annotations, and submit to Anthropic's Claude directory and to ChatGPT. The listing decision is theirs.
Maturity, by their own words
An MCP generator or platform (Speakeasy, Stainless, FastMCP, Zuplo, Cloudflare, APIMatic, Postman, Mintlify)
Stainless calls MCP generation experimental, APIMatic's generator is in alpha, and FastMCP recommends its converter for prototyping.
A custom connector built by Modern Mustard Seed
Nine of our own connectors are listed in Anthropic's Claude directory, and 15 servers are published in the official MCP Registry.
Price
An MCP generator or platform (Speakeasy, Stainless, FastMCP, Zuplo, Cloudflare, APIMatic, Postman, Mintlify)
Published on October 26, 2026: Stainless Free for up to 5 generators; FastMCP free and open source, its Gateway Developer plan $35 per developer a month plus usage; Zuplo Builder $25 a month; Mintlify Pro $450 a month billed annually; Cloudflare Workers Paid from a $5 monthly minimum. Speakeasy and APIMatic show no public price for MCP generation.
A custom connector built by Modern Mustard Seed
Set package price, quoted after a free discovery call
When an MCP generator is the better choice
- Your API is clean, documented in OpenAPI, and your engineers want to own the server.
- Your users are developers who want broad API coverage more than a few curated jobs.
- You already generate SDKs with Stainless or Speakeasy.
- You only want your docs searchable inside AI tools, which Mintlify generates from your docs site.
When we are the better choice
- You want the connector designed around what your customers ask Claude and ChatGPT to do.
- You want it ready for Anthropic's and OpenAI's review: annotations, docs, a privacy page and test accounts.
- Your roadmap is full and nobody on the team has taken a server through directory review.
- You want someone keeping it working as MCP, Claude and ChatGPT change.
Which one fits you
Pick: Generator
A developer-tools company whose users are engineers
Full API coverage matters more than curated jobs, and the team owns the code.
Pick: Custom
A field service software company whose customers are owners, not developers
A few well-designed jobs, OAuth for each customer, and approval before any write.
Pick: Generator
A team that wants its docs searchable in AI tools
Mintlify generates a docs search server on its free plan.
Pick: Custom
A company that wants a Claude directory listing on a date
The submission, the review paperwork and the fixes come with the build.
Talk it through with a team that has been through review.
One call about your API, and a set package price if a custom connector is the better path.
Book a Discovery CallCommon questions
Should a SaaS company generate its MCP server or have a custom Claude connector built?
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Generate it when your API is clean in OpenAPI, your engineers will own the server and your users want broad coverage. Have it built when the connector should be designed around a few jobs your customers do, pass directory review and ship without pulling engineers off the roadmap.
Do Speakeasy or Stainless submit to the Claude directory for you?
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Not on the pages we read on October 26, 2026. Speakeasy generates a Claude Desktop extension bundle, and Zuplo and FastMCP Gateway document connecting to Claude, but none of their pages describes help with Anthropic's directory submission.
What does Anthropic require to list a connector?
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Per its submission guide on October 26, 2026: a remote server over HTTPS; OAuth 2.0 when tools act on a user's account, or no authentication for public data; a title and a readOnlyHint or destructiveHint on every tool; and a documentation URL, privacy policy URL, icon and test credentials for reviewers. Anyone on a paid Claude plan can submit.
What does OpenAI require to list an app in ChatGPT?
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Per OpenAI's guidelines on October 26, 2026: a verified individual or organization, a stable public HTTPS endpoint, domain verification, no authentication or OAuth (the portal has no API key flow), a published privacy policy, and a reviewer test account without MFA plus five positive and three negative test cases and a video walkthrough.
Sources and method
Modern Mustard Seed wrote this comparison and is one of the options in it. Every fact about another company was read from that company's own website on October 26, 2026. Prices change; check the source before you buy.
- Speakeasy MCP overview
- Speakeasy OAuth for MCP
- Stainless MCP
- Stainless MCP docs
- Stainless pricing
- FastMCP OpenAPI integration
- Prefect FastMCP Gateway pricing
- Zuplo MCP servers
- Zuplo pricing
- Cloudflare remote MCP server guide
- Cloudflare Workers pricing
- APIMatic MCP server generator
- Postman MCP generator
- Mintlify MCP
- Mintlify pricing
- Anthropic: submitting a connector
- OpenAI: submission
- OpenAI: guidelines