BuildActions

MCP Connectors

Connect your agent to external tools using MCP servers.
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MCP actions connect your Synthflow agent to an external MCP server, giving the LLM access to tools hosted on that server. During a call, the agent decides when to invoke these tools based on the conversation context, similar to custom actions, but using the open MCP standard instead of a hand-configured HTTP request.

You can configure MCP servers in the UI or manage them through the MCP configuration API.

MCP action configuration in Synthflow

MCP actions are currently supported on prompt-based agents. Flow Designer support is not yet available.

How it works

  1. You create an MCP server in your workspace with its URL and credentials, then discover its tools.
  2. You attach the MCP server to an agent and select which tools the agent can use.
  3. During a call, the LLM sees the selected tools and invokes them when the conversation calls for it.

Each workspace can register multiple MCP servers.

Step 1: Create an MCP server

  1. Go to Actions in the sidebar.
  2. Select MCP Connectors and create a new one.
  3. Enter the Server URL, the HTTPS endpoint of your MCP server.
  4. Choose an authentication method, No Auth or Bearer Token, and provide the credentials.
  5. Click Discover Tools. Synthflow connects to the server and lists the available tools.

The server URL must use HTTPS. Plain HTTP endpoints are rejected.

Tools are not synced automatically. If your MCP server adds, removes, or updates tools, click Discover Tools again.

Step 2: Attach to an agent

  1. Open your agent and go to the Actions tab.
  2. Click Add Action during the call and select your MCP server.
  3. Select which tools the agent should have access to. Fewer tools means a smaller context window and better LLM performance.

The agent now has access to the selected MCP tools. During calls, the LLM will invoke them based on the conversation context.

If your MCP server exposes many tools, only select the ones relevant to this agent’s purpose. Large tool lists can degrade response quality and increase latency.

Error handling

ScenarioBehavior
MCP server unreachableAction is skipped for this call. The agent continues without the tools.
Tool call times outThe LLM handles the timeout and continues the conversation.
Non-success responseThe error is logged in call records. The LLM continues the conversation.
Invalid credentialsTool discovery fails with an authorization error. Check your server URL and credentials.

Synthflow cannot guarantee the response time of your MCP server. If your tools involve slow operations, such as database queries or third-party API chains, the LLM will handle the wait and continue the conversation.

Limitations

  • MCP actions are supported on prompt-based agents only. Flow Designer agent support is planned.
  • Streamable HTTP is the preferred transport. SSE (Server-Sent Events) is supported as a fallback for backward compatibility. stdio-based MCP servers are not compatible.

FAQ

No. MCP actions are currently supported on prompt-based agents only. Flow Designer support is planned.

No. If your MCP server adds, removes, or updates tools, open the MCP action and click Discover Tools again.

Yes. Use the MCP configuration API to manage workspace MCP servers programmatically.