MCP Server Replicate

Instructions

    Args:
        payload: The webhook payload to verify
        signature: The signature from the X-Replicate-Signature header
        secret: The webhook signing secret from get_webhook_secret

    Returns:
        True if signature is valid, False otherwise
    

Implementation Reference

• src/mcp_server_replicate/server.py:902-924 (handler)

  Core handler function for the 'verify_webhook' tool. Computes the expected HMAC-SHA256 signature from the serialized payload and secret, then compares it securely to the provided signature.

  @mcp.tool()
  def verify_webhook(payload: WebhookPayload, signature: str, secret: str) -> bool:
      """Verify that a webhook request came from Replicate using HMAC-SHA256.
  
      Args:
          payload: The webhook payload to verify
          signature: The signature from the X-Replicate-Signature header
          secret: The webhook signing secret from get_webhook_secret
  
      Returns:
          True if signature is valid, False otherwise
      """
      if not signature or not secret:
          return False
  
      # Convert payload to canonical JSON string
      payload_str = json.dumps(payload.model_dump(), sort_keys=True)
  
      # Calculate expected signature
      expected = hmac.new(secret.encode(), payload_str.encode(), hashlib.sha256).hexdigest()
  
      # Compare signatures using constant-time comparison
      return hmac.compare_digest(signature, expected)

• src/mcp_server_replicate/models/webhook.py:23-26 (schema)

  Pydantic model defining the structure of the 'payload' input parameter for verify_webhook tool.

  class WebhookPayload(BaseModel):
      """The full payload of a webhook request."""
      event: WebhookEvent
      prediction: Dict[str, Any] = Field(..., description="Full prediction object at time of event") 

• src/mcp_server_replicate/server.py:902-902 (registration)

  The @mcp.tool() decorator registers the verify_webhook function with the FastMCP server using the default name based on the function name.

  @mcp.tool()