Skip to main content
Connections are added inside an Access bundle. At claude.ai/admin-settings/claude-tag, open Access bundles in the left navigation, click into a bundle (or Create one), and go to its Credentials tab.
For a service that doesn’t have a preset Connect button, use Custom tool on the bundle’s Credentials tab. This works for any service with an HTTP API. The BigQuery guide is a worked example.

​
Add a custom HTTP API

​
What you need from the service

  • A service-account credential (an API key, token, or OAuth client), not your personal login
  • The API host (for example api.example.com)
  • How the API authenticates (which header or flow it expects)
See Create a dedicated account per service for the service-account patterns.

​
Fill out the Custom tool form

After saving, where the credential has an allow rule, you can narrow it by HTTP method and path from its Edit connection dialog; see Restrict by path or method.

​
Credential types

For GitHub repositories, use the GitHub connection at Configure GitHub access rather than a credential from this table. If you’re unsure which type, check the service’s API authentication docs for which header or flow it expects.

​
AWS SigV4

Use the AWS SigV4 credential type for AWS service APIs such as S3, Lambda, and DynamoDB. Agent Proxy reads the AWS service and signing region from the hostname and signs each outbound request with the credential at the boundary, so neither the model nor the sandbox holds the keys. Agent Proxy signs requests to hostnames in these forms:
  • service.region.amazonaws.com
  • S3 virtual-hosted-style endpoints, for example my-bucket.s3.us-east-1.amazonaws.com
  • Service hostnames with extra parts before the service name, as long as the region is the last part before amazonaws.com, for example the Amazon ECR API host api.ecr.us-east-1.amazonaws.com or the host of an API Gateway invoke URL, abc123.execute-api.us-east-1.amazonaws.com
  • The regionless hosts of IAM, STS, S3, Route 53, CloudFront, Organizations, and Global Accelerator, for example iam.amazonaws.com, which Agent Proxy signs for us-east-1
Requests to other hostnames fail before reaching AWS. Agent Proxy can’t sign a request to a hostname with no region for any other service, such as ec2.amazonaws.com, or to a hostname with the region before the service name, such as an OpenSearch domain endpoint (my-domain.us-east-1.es.amazonaws.com). It also can’t sign requests to an API Gateway custom domain or to a non-AWS API that uses Signature Version 4. Use long-lived credentials from a dedicated IAM user where you can. Temporary STS credentials work but expire on their own schedule, and the connection stops working when they do; you re-enter all three values to rotate. Claude can call the endpoint with curl, an AWS SDK, or the AWS CLI. The sandbox holds no real AWS credentials, so a CLI or SDK signs the request with placeholder values; Agent Proxy strips that signature and re-signs with the stored credential before the request leaves for AWS. The one shape it can’t re-sign is chunked payload signing. If Claude reports that chunked signing isn’t supported through the proxy, have it set payload_signing_enabled = false in ~/.aws/config and retry.

​
When AWS returns SignatureDoesNotMatch

A SignatureDoesNotMatch response from AWS means the request AWS received doesn’t match the one Agent Proxy signed. A dropped or expired session token is a different failure: AWS rejects it with a token error such as InvalidClientTokenId, not SignatureDoesNotMatch. Rotate all three fields.

​
OAuth 2.0 JWT bearer

Use the OAuth 2.0 JWT bearer credential type for APIs that exchange a JWT signed with your private key for an access token. The Salesforce guide is a worked example. The Private key (PEM) field takes a PEM-encoded RSA private key without a passphrase, the format that begins with -----BEGIN PRIVATE KEY----- or -----BEGIN RSA PRIVATE KEY-----. Identity providers such as Okta export the key as a JWK (a JSON object) by default; convert a JWK to PEM before pasting it. The form doesn’t check the key’s format, so a key in the wrong format fails only when you save.

​
When saving fails with “Failed to create egress credential”

Saving the form can return the error “Failed to create egress credential. Check your inputs and try again.” The most likely cause is a private key that isn’t PEM-encoded, for example a JWK pasted as-is into the Private key (PEM) field. Convert the key to PEM and save again. Saving also fails when a PEM-encoded key isn’t an RSA key or has a passphrase. Once the key is in the right format, re-check each field against the values from your service.

​
Add a custom MCP server

The server must be a remote endpoint that Claude can reach at a URL over the internet. An MCP server that runs on a person’s machine over stdio, including one packaged as a desktop extension, can’t be connected, because sessions run in a cloud sandbox that Anthropic hosts, not on anyone’s machine. Host the server as a remote endpoint first, then follow the steps below. To give Claude an MCP server (one you run, or a vendor’s hosted MCP endpoint), the pattern is a plugin plus a credential:
1

Add a plugin that declares the MCP server

In the bundle’s Plugins tab (or via your skills repository), add a plugin whose .mcp.json points at the server URL. The plugin tells Claude the server exists and how to call it.
2

Add a credential for the server's host

On the Credentials tab, click Connect next to Custom tool and add a credential for the MCP server’s host (for example, a Bearer token with Allowed websites set to your-mcp-host.example.com). This lets the call leave the sandbox with auth attached.
The plugin’s .mcp.json is loaded because it’s part of an attached plugin; an .mcp.json checked into a repository Claude clones is not loaded.

​
Verify the connection

In a channel under the bundle’s scope, in a new thread, ask Claude to make a small read against the API:
Check the service’s own audit log to confirm the call landed under your service account. New threads pick up the connection on their own; in an existing thread, ask Claude to use the service by name. If Claude reports that it can’t use the credential, check its status on the Access bundles page. Not active means no allow rule uses the credential yet. Approval needed means another admin submitted it through a shared setup link; select Review, then Approve. See Verify the connection saved.