Custom ChatGPT plugins for business
Custom ChatGPT plugins that connect your workspace to your business.
OpenAI now lets companies add their own plugins to ChatGPT, built on MCP. We build the plugin for your internal systems, set it up for your workspace admins, and make sure each person only reaches what they already can.
What you get
- An MCP server packaged as a custom ChatGPT plugin for your workspace
- Search and fetch tools so the plugin also works with company knowledge
- Admin setup in ChatGPT workspace settings, with role-based availability
- Per-user sign-in so ChatGPT only sees what each person can see
- Clear disclosure of the data and actions the plugin can reach
- Optional Claude connector from the same server, tested in both
What is a custom ChatGPT plugin?
A custom ChatGPT plugin connects ChatGPT to a system your company runs, such as an internal database, a knowledge base, or a line-of-business app. OpenAI's plugins, previously called connectors and apps, are built on the Model Context Protocol, so a custom plugin is an MCP server that ChatGPT calls when a question needs it.
On Business and Enterprise workspaces, admins decide which plugins are available, who can use them, and what actions they may take. Users then summon the plugin in a conversation and ChatGPT answers with live data instead of whatever was pasted in.
Because the plugin is an MCP server, the same build can usually serve Claude as a custom connector too. That keeps your access rules in one place no matter which assistant your team prefers.
Where it pays off
Company knowledge from private systems
Bring wikis, policies, and records that ChatGPT's built-in plugins cannot reach into the same company knowledge search your team already uses.
Sales and account questions
Let reps ask about an account's orders, tickets, and contract terms across systems that have no off-the-shelf plugin.
Finance and operations lookups
Answer questions about invoices, stock levels, schedules, or job status from the system of record, with the source named in the answer.
Actions with approval
Create a record or start a process from a conversation, with write actions labeled so ChatGPT asks before it acts.
How we build it
Scope the plugin
We confirm your ChatGPT plan and admin settings, list the questions and actions, and agree what the plugin will disclose to users.
Build on MCP
We build the MCP server, with search and fetch tools for knowledge use and narrow tools for everything else, and test it in your ChatGPT workspace before anyone relies on it.
Publish to your workspace
We work with your admin to add and publish the plugin, set who can use it, and check it against your data rules.
Support it
We host and maintain it, and keep it current as OpenAI changes how plugins are configured and reviewed.
Custom GPT, built-in plugin, or custom plugin
A Custom GPT is a set of instructions and uploaded files. A plugin is a live connection. A custom plugin is that live connection to a system no vendor has covered.
| Criterion | Custom GPT | Built-in plugin | Custom plugin from Prestyj |
|---|---|---|---|
| Live data | No, uploaded files | Yes, for that vendor's app | Yes, for your systems |
| Private or in-house systems | No | Rarely | Yes |
| Per-user permissions | No | Vendor dependent | Yes, enforced server-side |
| Also usable in Claude | No | Separate setup | Same MCP server |
| Admin control | Sharing settings | Workspace settings | Workspace settings |
MCP servers we have built
Built and tested by Prestyj. Client names withheld.
Portfolio data connector for an investment firm
Yardi via Power BI · Monday.com · SharePoint
A remote, read-only MCP server that answers portfolio questions from evidence-backed records across three source systems.
- Streamable HTTP endpoint with OAuth protected-resource metadata and a delegated, API-scoped token per user
- Denied data is reported as withheld, never guessed or filled from another source
- Conflicting sources are shown side by side with their evidence instead of being averaged
- Server instructions kept under the 2,048 character limit Claude Code applies, enforced by a test
Connect-once business memory over MCP
Monday.com · Yardi · SharePoint · Postgres
Syncs a company's apps into typed facts in Postgres once, then hands them to any AI client over MCP.
- Six tools: schema, brief, read-only SQL with a five second cap, document search, open conflicts, and resolve conflict
- When sources disagree, a person answers once and the answer becomes a rule
- Works in Claude Desktop, Claude Code, and any other MCP host
Governed context server for a research platform
Versioned context API · Webhooks
A stdio MCP server with 24 workflow-specific tools that never sees a database URL or tenant ID.
- The API key resolves the tenant; caller-supplied tenant or access fields are rejected before execution
- Every tool enforces a scope plus result, time, output-token, and cost ceilings
- Read-only by default; writes need a separate switch, explicit confirmation, and an idempotency key
- A tool-selection benchmark checks that the model picks the right tool for each question
Multi-tenant MCP for isolated customer deployments
Per-customer deployment · Per-customer database
One codebase deployed separately for each customer, with an MCP endpoint whose tool catalog comes from that customer's configuration.
- OAuth token introspection with a dedicated read scope
- Per-token rate limits and bounded request sizes
- No customer data or secrets in the shared code or deployment packs
Questions we get
Read more
Guides
- Claude connectors vs ChatGPT plugins: one MCP server, two assistantsHow Claude custom connectors and ChatGPT custom plugins compare for business use, what they share through MCP, where admin controls and plan rules differ, and how to serve both from one server.
- MCP server security checklist for businessesA practical security checklist for businesses deploying a custom MCP server for Claude or ChatGPT: authentication, server-side authorization, tool design, limits, logging, and testing.
- How to build a custom ChatGPT plugin for your companyHow companies build a custom ChatGPT plugin today: an MCP server, OpenAI's plugin docs, which ChatGPT plans allow custom MCP servers, admin publishing and RBAC, and testing before rollout.
- Read-only first: designing safe write actions and approvals in an AI connectorHow to add write actions to a Claude connector or ChatGPT plugin safely: start read-only, annotate tools honestly, require confirmation, prevent duplicate writes, and keep checks in the server.
Related services
- Custom MCP serversOne well-built MCP server gives Claude, ChatGPT, Cursor, and your own agents the same governed access to your data and actions. We design it around your workflows, secure it like any other production API, and run it.
- Custom Claude connectorsThe Claude directory covers the popular SaaS apps. Your ERP, your database, your internal API, and the spreadsheet that runs operations usually have no connector at all. We build one, host it, and roll it out to your Claude Team or Enterprise workspace.
- Done-for-you Claude connectorsMost teams do not want an MCP project. They want Claude to know their customers, orders, files, and numbers by next month. We take the whole job: scoping, build, hosting, security, rollout, and upkeep.
Connectors by system
Tell us what Claude or ChatGPT should know.
Bring the questions your team asks and the systems that hold the answers. We will come back with a written scope, a timeline, and a fixed price.