# Call the agent

Before calling an agent, obtain its Agent Card; then you can use the A2A or MCP protocol to initiate the call.

## Choose a task

| Task | Description |
| --- | --- |
| [Get the agent call instructions](https://omnifabric.cloudsigma.com/docs/reference/api/ai-studio/agents/agent-invocation/get-agent-card.html.md) | Read the Agent Card and confirm the A2A protocol version, calling address, input and output type and capability supported by the target agent. |
| [Called by other agents](https://omnifabric.cloudsigma.com/docs/reference/api/ai-studio/agents/agent-invocation/call-agent-from-agent.html.md) | Send messages or query tasks to target agents via A2A JSON-RPC. |
| [Called from MCP client](https://omnifabric.cloudsigma.com/docs/reference/api/ai-studio/agents/agent-invocation/call-agent-from-mcp-client.html.md) | Use a task-scoped RuntimeGrant to list or call the tools allowed for the current task over MCP. |