MCP Server
Connecting Clients
Configure popular MCP clients to talk to the SignatureAPI MCP server.
Every MCP-compatible client needs the same two things: the server URL and a way to perform the OAuth sign-in flow. Once you provide the URL, the client handles discovery, registration, and the redirect to SignatureAPI for you.
https://mcp.signatureapi.com/mcpThe first time you connect, a browser window opens where you sign in to SignatureAPI and approve the connection. After that, the client refreshes its token automatically.
Network access
Before configuring any client, make sure outbound HTTPS traffic to *.signatureapi.com is allowed on the network where the client runs. Corporate proxies, VPNs, firewalls, and AI sandbox environments that block these hosts will cause the connection or sign-in to fail.
Claude Desktop
- Open Settings → Connectors → Add custom connector.
- Name the connector “SignatureAPI” and enter the server URL above.
- Save. A browser window opens for sign-in. Approve the connection.
The SignatureAPI tools become available in any conversation. You can pin frequently used envelopes from the side panel.
Claude.ai
- From any chat, open Connectors → Add custom connector.
- Enter the server URL above and save.
- Complete the SignatureAPI sign-in when prompted.
Pure connector clients like Claude.ai do not execute code locally. When uploading documents, supply a publicly accessible URL on an allowlisted host (S3, Google Drive, Dropbox, and similar). See Uploading files.
ChatGPT
Custom MCP connectors require a paid plan (Plus, Pro, Team, Enterprise, or Edu) and ChatGPT’s Developer mode, which is currently in beta.
While SignatureAPI’s MCP server is in private beta, you need to add it as a custom connector using the steps below. Once it is generally available, we will publish it to ChatGPT Apps so you can install it directly without the developer mode flow.
- Open Settings → Connectors → Advanced and turn on Developer mode. ChatGPT shows a warning that custom connectors run third-party code on your behalf; accept it. You only do this once.
- Go to Settings → Connectors → Add new connector.
- Give the connector a name (for example, “SignatureAPI”) and paste the server URL above.
- Set the authentication mode to OAuth, confirm you trust the application, and click Create.
- Complete the SignatureAPI sign-in in the popup.
To use the connector in a chat, click the + icon in the message composer, choose More → Developer mode, and toggle SignatureAPI on for that conversation.
As with Claude.ai, ChatGPT cannot run a local PUT. Reference documents by URL.
Claude Code
From the command line:
claude mcp add --transport http signatureapi https://mcp.signatureapi.com/mcpThen, inside Claude Code, run /mcp and complete the sign-in flow. Envelopes become reachable through the @signatureapi resource picker.
Generic configuration
For any MCP client that accepts a Streamable HTTP server:
| Field | Value |
|---|---|
| Transport | http (Streamable HTTP) |
| URL | https://mcp.signatureapi.com/mcp |
| Auth | OAuth 2.1 (the client handles it) |
If the client does not implement OAuth Dynamic Client Registration, see Authorization for the discovery endpoints and the patterns available for service providers.
Verifying the connection
After connecting, ask the agent to call list_envelopes. A successful response with your account’s envelopes confirms the OAuth flow and account scoping are correct.
If the call returns “Application has been disconnected,” the connection was revoked from the dashboard. Reconnect by removing and re-adding the server in your client.