Dynamically Header passing to a Tool

progressive-amaranth · 2025-05-26T14:34:22.317Z

I am building a voice bot using VAPI. I would like to dynamically pass the header to the tool. How can I achieve this? Since each user has a different token that I need to pass to the tool as a header, I’m unable to set it directly from the Vapi Dashboard.

V

Vapi Support BotAPP•5/26/25, 2:35 PM

Vapi currently supports setting static headers for tools, but does not document a way to dynamically inject per-user headers (like a user token) directly from the Dashboard. The typical approach is to have Vapi send the payload to your backend, where you add the dynamic header before calling the actual tool.

Clarifying question:
Are you able to route tool calls through your own backend, so you can programmatically add the user-specific token to the headers before forwarding the request to the tool?

Sources:

⤵️ Mention @Vapi Support Bot for follow-ups 🐥

P

progressive-amaranthOP•5/26/25, 2:39 PM

I need a way to pass the authentication token of a specific user to the tool, so that I can identify which user is making the tool call. Can't I do it using crendentials endpoint, if yes, can you explain how.

V

Vapi Support BotAPP•5/26/25, 2:41 PM

You should route tool calls through your own backend, where you can inject the user-specific authentication token into the headers before forwarding the request to the actual tool. Here’s a simple Node.js/Express example:

app.post('/vapi-tool-proxy', async (req, res) => {
  const userToken = /* logic to get user token from session/context */;
  const response = await fetch('https://your-tool-endpoint', {
    method: 'POST',
    headers: {
      'Authorization': `Bearer ${userToken}`,
      'Content-Type': 'application/json'
    },
    body: JSON.stringify(req.body)
  });
  res.status(response.status).send(await response.text());
});

app.post('/vapi-tool-proxy', async (req, res) => {
  const userToken = /* logic to get user token from session/context */;
  const response = await fetch('https://your-tool-endpoint', {
    method: 'POST',
    headers: {
      'Authorization': `Bearer ${userToken}`,
      'Content-Type': 'application/json'
    },
    body: JSON.stringify(req.body)
  });
  res.status(response.status).send(await response.text());
});

app.post('/vapi-tool-proxy', async (req, res) => {
  const userToken = /* logic to get user token from session/context */;
  const response = await fetch('https://your-tool-endpoint', {
    method: 'POST',
    headers: {
      'Authorization': `Bearer ${userToken}`,
      'Content-Type': 'application/json'
    },
    body: JSON.stringify(req.body)
  });
  res.status(response.status).send(await response.text());
});

app.post('/vapi-tool-proxy', async (req, res) => {
  const userToken = /* logic to get user token from session/context */;
  const response = await fetch('https://your-tool-endpoint', {
    method: 'POST',
    headers: {
      'Authorization': `Bearer ${userToken}`,
      'Content-Type': 'application/json'
    },
    body: JSON.stringify(req.body)
  });
  res.status(response.status).send(await response.text());
});

Set your tool's server URL in Vapi to this proxy endpoint.
This is the standard way to handle dynamic per-user headers in Vapi.

Sources:

P

progressive-amaranthOP•5/26/25, 2:42 PM

I want to do it in python. Moreover, "how can I get user token from session/context"?

V

Vapi Support BotAPP•5/26/25, 2:43 PM

To dynamically pass a user-specific token as a header in Python, set your tool's server URL in Vapi to a proxy endpoint on your backend. In your Flask app, inject the token before forwarding the request:

from flask import Flask, request
import requests

app = Flask(__name__)

@app.route('/vapi-tool-proxy', methods=['POST'])
def proxy():
    user_token = "EXTRACTED_USER_TOKEN"  # Implement your logic here
    resp = requests.post(
        'https://your-tool-endpoint',
        headers={'Authorization': f'Bearer {user_token}', 'Content-Type': 'application/json'},
        json=request.get_json()
    )
    return (resp.text, resp.status_code, resp.headers.items())

# Run your Flask app as usual

from flask import Flask, request
import requests

app = Flask(__name__)

@app.route('/vapi-tool-proxy', methods=['POST'])
def proxy():
    user_token = "EXTRACTED_USER_TOKEN"  # Implement your logic here
    resp = requests.post(
        'https://your-tool-endpoint',
        headers={'Authorization': f'Bearer {user_token}', 'Content-Type': 'application/json'},
        json=request.get_json()
    )
    return (resp.text, resp.status_code, resp.headers.items())

# Run your Flask app as usual

from flask import Flask, request
import requests

app = Flask(__name__)

@app.route('/vapi-tool-proxy', methods=['POST'])
def proxy():
    user_token = "EXTRACTED_USER_TOKEN"  # Implement your logic here
    resp = requests.post(
        'https://your-tool-endpoint',
        headers={'Authorization': f'Bearer {user_token}', 'Content-Type': 'application/json'},
        json=request.get_json()
    )
    return (resp.text, resp.status_code, resp.headers.items())

# Run your Flask app as usual

from flask import Flask, request
import requests

app = Flask(__name__)

@app.route('/vapi-tool-proxy', methods=['POST'])
def proxy():
    user_token = "EXTRACTED_USER_TOKEN"  # Implement your logic here
    resp = requests.post(
        'https://your-tool-endpoint',
        headers={'Authorization': f'Bearer {user_token}', 'Content-Type': 'application/json'},
        json=request.get_json()
    )
    return (resp.text, resp.status_code, resp.headers.items())

# Run your Flask app as usual

How to get the user token: You must design your system to make the token available (e.g., include it in the payload or retrieve it from your own session/context), as Vapi does not provide it automatically in the request.

Sources:

V

VapiAPP•5/27/25, 5:48 PM

Include the token in assistantOverrides.variableValues when initiating the call, then reference it in the tool’s headers using {{userToken}}.

Dynamically Header passing to a Tool

Similar Threads

Similar Threads

Similar Threads