Connect CompanyBook to your AI

4 short steps, about 5 minutes. You sign in with your account, no API key needed.

First you need a free account with a confirmed email. Create account Log in

Where will you use it?

Web and desktop

Connect in ChatGPT Step 1 of 4

Use chatgpt.com or the ChatGPT desktop app. Open ChatGPT in a new tab, then press:

Plugins Add Add custom MCP server
Open ChatGPT
No Add custom MCP server option? Your plan or workspace may not allow custom connectors yet. On a work account, ask your admin.

Optional: install the CompanyBook pluginThe plugin adds skills: ready-made workflows for researching a company, comparing companies, finding prospects and filling in a company list from CSV or Excel.

Why add them

The full picture from one request.Your assistant follows a set method for each job, so you do not have to explain what to check.
Your allowance goes further.It skips duplicates, reuses what it already found and asks you before a big job.
Your files stay in order.It fills in your CSV or Excel list and keeps your rows and columns as they are.

Open Terminal and run this. It downloads the package and adds it to the ChatGPT app.

mkdir -p "$HOME/companybook-plugins" &&
curl -fsSL https://downloads.companybook.bg/companybook.zip -o "$HOME/companybook-plugins/companybook.zip" &&
rm -rf "$HOME/companybook-plugins/companybook" &&
unzip -q "$HOME/companybook-plugins/companybook.zip" -d "$HOME/companybook-plugins/companybook" &&
rm "$HOME/companybook-plugins/companybook.zip" &&
mkdir -p "$HOME/.agents/plugins" &&
if [ -e "$HOME/.agents/plugins/marketplace.json" ] && ! grep -q companybook-local "$HOME/.agents/plugins/marketplace.json"; then
  echo "You already have a plugin list at ~/.agents/plugins/marketplace.json, so it was not changed. Ask your assistant to add CompanyBook to it."
else
  cat > "$HOME/.agents/plugins/marketplace.json" <<'JSON'
{
  "name": "companybook-local",
  "plugins": [
    {
      "name": "companybook",
      "source": { "source": "local", "path": "./companybook-plugins/companybook" },
      "policy": { "installation": "AVAILABLE", "authentication": "ON_INSTALL" },
      "category": "Productivity"
    }
  ]
}
JSON
fi

2
Restart the ChatGPT desktop app. Open Plugins, choose companybook-local and install CompanyBook.
3
Sign in to CompanyBook when asked, then start a new chat.

This works in the ChatGPT desktop app. On chatgpt.com, a workspace admin has to publish the package first. Installing it also connects CompanyBook, so remove the plugin you created above to avoid seeing the tools twice. Run the command again to get a newer version.

Connect in Claude Step 1 of 4

Set it up on claude.ai or in the Claude desktop app. It then works in the Claude mobile app too. Open Claude in a new tab, then press:

Customize Connectors + Add Add custom connector
Open Claude
On a Team or Enterprise plan, an owner may need to allow custom connectors first. If your Mac offers to install command line developer tools, click Cancel: CompanyBook does not need them.

Optional: install the CompanyBook pluginThe plugin adds skills: ready-made workflows for researching a company, comparing companies, finding prospects and filling in a company list from CSV or Excel.

Why add them

The full picture from one request.Your assistant follows a set method for each job, so you do not have to explain what to check.
Your allowance goes further.It skips duplicates, reuses what it already found and asks you before a big job.
Your files stay in order.It fills in your CSV or Excel list and keeps your rows and columns as they are.

1
Download the package. Keep it as a ZIP file.
Download the plugin (ZIP)
2
In the Claude desktop app, open Customize, then Plugins. Click Add, then Upload plugin, and choose companybook.zip.
3
Start a new chat and ask for a company report.

This works in the Claude desktop app and stays on that computer. Keep the connector you added above, and on a work account ask your admin if you cannot upload plugins. If Safari unzipped the download, turn off Open "safe" files after downloading in Safari Settings, under General, and download it again.

Connect in Claude Code

Documentation

For people who use Claude Code in the terminal.

Add CompanyBook:

claude mcp add --transport http --scope user companybook https://api.companybook.bg/mcp

2

Start Claude Code, type /mcp, choose companybook, then Authenticate.
3

Your browser opens. Sign in to CompanyBook and click Connect account.

Optional: install the CompanyBook pluginThe plugin adds skills: ready-made workflows for researching a company, comparing companies, finding prospects and filling in a company list from CSV or Excel.

Why add them

The full picture from one request.Your assistant follows a set method for each job, so you do not have to explain what to check.
Your allowance goes further.It skips duplicates, reuses what it already found and asks you before a big job.
Your files stay in order.It fills in your CSV or Excel list and keeps your rows and columns as they are.

Open Terminal and run this. It downloads the package.

mkdir -p "$HOME/companybook-plugins" &&
curl -fsSL https://downloads.companybook.bg/companybook.zip -o "$HOME/companybook-plugins/companybook.zip" &&
rm -rf "$HOME/companybook-plugins/companybook" &&
unzip -q "$HOME/companybook-plugins/companybook.zip" -d "$HOME/companybook-plugins/companybook" &&
rm "$HOME/companybook-plugins/companybook.zip"

2
Start Claude Code with the skills. Use this command each time you want them.
```
claude --plugin-dir "$HOME/companybook-plugins/companybook"
```

Run the first command again to get a newer version.

Connect in Codex

Documentation

For people who use the Codex command line.

Add CompanyBook:

codex mcp add companybook --url https://api.companybook.bg/mcp \
  --oauth-client-id https://chatgpt.com/oauth/codex/client.json \
  --oauth-resource https://api.companybook.bg/mcp

2
Sign in. Your browser opens: sign in to CompanyBook and click Connect account.
```
codex mcp login companybook --scopes account:read,company:read
```
3

Start a new Codex session.

Optional: install the CompanyBook pluginThe plugin adds skills: ready-made workflows for researching a company, comparing companies, finding prospects and filling in a company list from CSV or Excel.

Why add them

The full picture from one request.Your assistant follows a set method for each job, so you do not have to explain what to check.
Your allowance goes further.It skips duplicates, reuses what it already found and asks you before a big job.
Your files stay in order.It fills in your CSV or Excel list and keeps your rows and columns as they are.

Open Terminal and run this. It downloads the package and adds it to Codex.

mkdir -p "$HOME/companybook-plugins" &&
curl -fsSL https://downloads.companybook.bg/companybook.zip -o "$HOME/companybook-plugins/companybook.zip" &&
rm -rf "$HOME/companybook-plugins/companybook" &&
unzip -q "$HOME/companybook-plugins/companybook.zip" -d "$HOME/companybook-plugins/companybook" &&
rm "$HOME/companybook-plugins/companybook.zip" &&
mkdir -p "$HOME/.agents/plugins" &&
if [ -e "$HOME/.agents/plugins/marketplace.json" ] && ! grep -q companybook-local "$HOME/.agents/plugins/marketplace.json"; then
  echo "You already have a plugin list at ~/.agents/plugins/marketplace.json, so it was not changed. Ask your assistant to add CompanyBook to it."
else
  cat > "$HOME/.agents/plugins/marketplace.json" <<'JSON'
{
  "name": "companybook-local",
  "plugins": [
    {
      "name": "companybook",
      "source": { "source": "local", "path": "./companybook-plugins/companybook" },
      "policy": { "installation": "AVAILABLE", "authentication": "ON_INSTALL" },
      "category": "Productivity"
    }
  ]
}
JSON
fi

2
Install it, and sign in to CompanyBook when asked:
```
codex plugin add companybook@companybook-local
```
3
Restart Codex and start a new session.

Installing the package also connects CompanyBook. If you followed the steps above, first run codex mcp remove companybook, so the tools do not appear twice. Run the first command again to get a newer version.

Check that it works

Start a new chat and ask:

If your assistant tells you how many requests you have left, you are all set.

Then ask, for example

Ask in Bulgarian or English, and change the details to fit what you need.

The registry does not publish the shareholders of a joint-stock company (АД), so a question about who owns one may have no answer.

Prefer your AI to guide you?

Copy one message into a new chat and your assistant goes through the steps with you.

Copy and open ChatGPT Copy and open Claude

Read the full message

Help me connect CompanyBook to my AI app. CompanyBook (companybook.bg) has data on every Bulgarian company, and it offers a connector (an MCP server) and optional skills for AI apps. Reply in the language I write in. I'm not technical, so keep it simple and give me one step at a time.

The exact steps for each app are at the end of this message. They are current, so use them as written. Don't search the web for other steps, and don't tell me you can't confirm them. If my screen doesn't match a step, ask me what I see. Don't tell me my plan can't do this, even if a help article says so: have me check the menu first, because a free ChatGPT account can have this option too.

1. ASK WHICH APP
Ask me which app we are in: the ChatGPT desktop app, chatgpt.com, Claude, Claude Code or Codex. Don't work it out yourself, because the ChatGPT desktop app can look like Codex from the inside.

2. ASK TWO MORE THINGS
Ask if I also want the skills: ready-made workflows for researching a company, comparing companies, finding prospects and filling in a company list.
Ask if I have set up CompanyBook in this app before. If I have, remove the old setup first. In ChatGPT, delete CompanyBook under Plugins. In Claude, remove it under Customize, then Connectors. In Claude Code, run claude mcp remove companybook. In Codex, run codex mcp remove companybook. In ChatGPT and Codex, if the codex command exists, also run codex plugin marketplace remove companybook-local. An error from these two commands only means there was nothing to remove.

3. SET IT UP
Follow the steps for my app. In the ChatGPT desktop app and Codex, the skills package also connects CompanyBook, so if I want the skills there, skip the connection steps and do only the skills steps.
If you can run commands on my computer here, run the terminal steps yourself as soon as I say yes, and tell me what you did. Don't ask me to paste them. If you can't run commands, say so once and give me each command to paste into Terminal. Try before you say something can't be done, and never say you ran something you didn't.
I need a CompanyBook account with a confirmed email address. If I don't have one, I create a free account at https://companybook.bg/sign-up first. During sign-in, a companybook.bg page shows which account will be connected: I check it's mine and click "Connect account". There is no API key to paste. If sign-in shows an error, ask me to copy only the error message, never the browser address.

4. CHECK IT IN A NEW CHAT
CompanyBook may not appear in this chat even when the setup worked, so we check in a new chat. Tell me to start a new chat, or a new session in Codex and Claude Code. In ChatGPT, I type @ and pick CompanyBook. Then I ask: "How much of my CompanyBook allowance is left today?"
If I get a number of requests, we are done. If not, tell me to come back to this chat, then check together that CompanyBook is switched on, that I signed in with the right account and that its email is confirmed. I can see my connections at https://companybook.bg/account/connections.

STEPS FOR EACH APP

### ChatGPT
Use chatgpt.com or the ChatGPT desktop app.
Connect:
1. Open Plugins, click Add, then Add custom MCP server.
2. Name it CompanyBook and paste this URL. Set authentication to OAuth and leave the client ID and secret empty.
https://api.companybook.bg/mcp
3. Tick "I understand and want to continue", then choose Create as a plugin. Click Connect CompanyBook, sign in to CompanyBook and click Connect account.
4. If you see Install on the new CompanyBook plugin, click it. In a new chat, type @ and pick CompanyBook.
No Add custom MCP server option? Your plan or workspace may not allow custom connectors yet. On a work account, ask your admin.
Skills:
1. Open Terminal and run this. It downloads the package and adds it to the ChatGPT app.
mkdir -p "$HOME/companybook-plugins" &&
curl -fsSL https://downloads.companybook.bg/companybook.zip -o "$HOME/companybook-plugins/companybook.zip" &&
rm -rf "$HOME/companybook-plugins/companybook" &&
unzip -q "$HOME/companybook-plugins/companybook.zip" -d "$HOME/companybook-plugins/companybook" &&
rm "$HOME/companybook-plugins/companybook.zip" &&
mkdir -p "$HOME/.agents/plugins" &&
if [ -e "$HOME/.agents/plugins/marketplace.json" ] && ! grep -q companybook-local "$HOME/.agents/plugins/marketplace.json"; then
echo "You already have a plugin list at ~/.agents/plugins/marketplace.json, so it was not changed. Ask your assistant to add CompanyBook to it."
else
cat > "$HOME/.agents/plugins/marketplace.json" <<'JSON'
{
"name": "companybook-local",
"plugins": [
{
"name": "companybook",
"source": { "source": "local", "path": "./companybook-plugins/companybook" },
"policy": { "installation": "AVAILABLE", "authentication": "ON_INSTALL" },
"category": "Productivity"
}
]
}
JSON
fi
2. Restart the ChatGPT desktop app. Open Plugins, choose companybook-local and install CompanyBook.
3. Sign in to CompanyBook when asked, then start a new chat.
This works in the ChatGPT desktop app. On chatgpt.com, a workspace admin has to publish the package first. Installing it also connects CompanyBook, so remove the plugin you created above to avoid seeing the tools twice. Run the command again to get a newer version.

### Claude
Set it up on claude.ai or in the Claude desktop app. It then works in the Claude mobile app too.
Connect:
1. Open Customize, then Connectors. Click + Add, then Add custom connector.
2. Name it CompanyBook and paste this URL.
https://api.companybook.bg/mcp
3. Choose Sign in now and Use Claude's published identity, then click Add. Click Connect, sign in to CompanyBook and click Connect account.
4. Start a new chat. Open the tools menu and check that CompanyBook is switched on.
On a Team or Enterprise plan, an owner may need to allow custom connectors first. If your Mac offers to install command line developer tools, click Cancel: CompanyBook does not need them.
Skills:
1. Download the package. Keep it as a ZIP file. https://downloads.companybook.bg/companybook.zip
2. In the Claude desktop app, open Customize, then Plugins. Click Add, then Upload plugin, and choose companybook.zip.
3. Start a new chat and ask for a company report.
This works in the Claude desktop app and stays on that computer. Keep the connector you added above, and on a work account ask your admin if you cannot upload plugins. If Safari unzipped the download, turn off Open "safe" files after downloading in Safari Settings, under General, and download it again.

### Claude Code
For people who use Claude Code in the terminal.
Connect:
1. Add CompanyBook:
claude mcp add --transport http --scope user companybook https://api.companybook.bg/mcp
2. Start Claude Code, type /mcp, choose companybook, then Authenticate.
3. Your browser opens. Sign in to CompanyBook and click Connect account.
Skills:
1. Open Terminal and run this. It downloads the package.
mkdir -p "$HOME/companybook-plugins" &&
curl -fsSL https://downloads.companybook.bg/companybook.zip -o "$HOME/companybook-plugins/companybook.zip" &&
rm -rf "$HOME/companybook-plugins/companybook" &&
unzip -q "$HOME/companybook-plugins/companybook.zip" -d "$HOME/companybook-plugins/companybook" &&
rm "$HOME/companybook-plugins/companybook.zip"
2. Start Claude Code with the skills. Use this command each time you want them.
claude --plugin-dir "$HOME/companybook-plugins/companybook"
Run the first command again to get a newer version.

### Codex
For people who use the Codex command line.
Connect:
1. Add CompanyBook:
codex mcp add companybook --url https://api.companybook.bg/mcp \
--oauth-client-id https://chatgpt.com/oauth/codex/client.json \
--oauth-resource https://api.companybook.bg/mcp
2. Sign in. Your browser opens: sign in to CompanyBook and click Connect account.
codex mcp login companybook --scopes account:read,company:read
3. Start a new Codex session.
Skills:
1. Open Terminal and run this. It downloads the package and adds it to Codex.
mkdir -p "$HOME/companybook-plugins" &&
curl -fsSL https://downloads.companybook.bg/companybook.zip -o "$HOME/companybook-plugins/companybook.zip" &&
rm -rf "$HOME/companybook-plugins/companybook" &&
unzip -q "$HOME/companybook-plugins/companybook.zip" -d "$HOME/companybook-plugins/companybook" &&
rm "$HOME/companybook-plugins/companybook.zip" &&
mkdir -p "$HOME/.agents/plugins" &&
if [ -e "$HOME/.agents/plugins/marketplace.json" ] && ! grep -q companybook-local "$HOME/.agents/plugins/marketplace.json"; then
echo "You already have a plugin list at ~/.agents/plugins/marketplace.json, so it was not changed. Ask your assistant to add CompanyBook to it."
else
cat > "$HOME/.agents/plugins/marketplace.json" <<'JSON'
{
"name": "companybook-local",
"plugins": [
{
"name": "companybook",
"source": { "source": "local", "path": "./companybook-plugins/companybook" },
"policy": { "installation": "AVAILABLE", "authentication": "ON_INSTALL" },
"category": "Productivity"
}
]
}
JSON
fi
2. Install it, and sign in to CompanyBook when asked:
codex plugin add companybook@companybook-local
3. Restart Codex and start a new session.
Installing the package also connects CompanyBook. If you followed the steps above, first run codex mcp remove companybook, so the tools do not appear twice. Run the first command again to get a newer version.

Your assistant cannot click for you, but where your app allows it, it can run the install for you. If it gets stuck, choose your app here and follow the steps yourself. If your Mac offers to install command line developer tools, click Cancel: CompanyBook does not need them.

If something goes wrong

I do not see CompanyBook in my chat. Start a new chat. Then check that CompanyBook is switched on in your app’s tools or connectors menu.
I cannot find the option to add a connector. Some plans and work accounts do not allow custom connectors. Check your plan, or ask your workspace admin.
Sign-in fails or says access denied. Make sure you signed in with the right CompanyBook account and that its email address is confirmed. Then connect again.
Can I use my CompanyBook API key? No. The connector works only with sign-in. Your API key still works with the regular CompanyBook API.
My assistant mentions “concurrency_limit”. It asked for too much at once. Nothing was charged: wait a moment and ask again.
I have used up my daily allowance. It resets overnight, Bulgarian time. For more, see the paid plans. See plans
Does the AI app see my password? No. You sign in on companybook.bg, and the app only gets permission to read company data for you. You can disconnect it at any time. Manage connections
How does the connection use my data? We explain it in plain words on a separate page. Read about the connection and your data

Limits

Every account gets a daily allowance. It resets overnight, Bulgarian time.

100 requests a day. Each search or company lookup counts as one.
100 companies a day. Opening the same company again that day does not count twice.
30 financial years a day. One company's statements for one year count as one.
0 for region and activity lookups. These never use your allowance.

2025 financial statements and the advanced search filters (revenue, profit, registration date and more) need a paid plan. See plans

For developers

REST API documentation Authentication llms.txt Model Context Protocol

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