cancel_task
Cancel a running task on an A2A agent.
LABSCO SUMMARY
Your client stops being the only agent in the conversation.
The bridge is deliberately thin: register a URL, send a message, poll or stream the result, cancel if it drags. That thinness is the point — nothing here interprets what the far side does, so the behaviour you get is the remote agent's rather than the bridge's. Sending and streaming are separate tools rather than one tool with a flag, so how the reply arrives is decided at call time.
What it is
A bridge between an MCP client and A2A agents, seven tools for registering agents and exchanging messages and tasks with them.
What you get
- Agents registered by URL, listed back, and unregistered when they retire
- Messages sent to a named agent, carrying a session id so an exchange can be more than one turn
- The same message streamed instead, for answers long enough that waiting for the whole of it is the wrong shape
- A task's result collected afterwards by task id, with as much of its history as you ask for
- A running task cancelled on the agent that is running it
Requirements
uv with a Python interpreter available — UV_PYTHON selects which one — and at least one reachable A2A agent whose URL you can register. Agents are addressed by that URL, so nothing works until one is running. Apache-2.0.
Setup effort
One command — uvx a2a-mcp-server
USE CASES
01
Handing a job to another team's agent
Register the agent's URL once, send it the request with a session id so follow-ups stay in the same thread, then collect the result by task id when it is ready rather than holding the conversation open.
02
Watching a long answer arrive as it is written
Streaming is a separate tool rather than a flag, so the choice between a single reply and a stream is made per message — useful when the far side takes long enough that silence is indistinguishable from failure.
03
Clearing out work and agents you no longer need
List what is currently registered, stop the task that is still running on one of them, and unregister the agent itself when the integration is finished with.
7 tools
Counted once with only startup setup. Other versions, modes or optional credentials may expose a different list.
get_task_result
Retrieve the result of a task from an A2A agent.
list_agents
List all registered A2A agents.
Returns: List of registered agents
register_agent
Register an A2A agent with the bridge server.
send_message
Send a message to an A2A agent.
send_message_stream
Send a message to an A2A agent and stream the response.
unregister_agent
Unregister an A2A agent from the bridge server.
BEFORE YOU INSTALL
What to know first
Tools you get
7 tools when we connected.
Requires
- uvx on PATH
- A running A2A agent whose URL you can register
CONTEXT COST
Light Standing cost
Rated by the size of the 7 tool definitions that ride along on every turn, not by how many there are
INSTALLATION
Connect your client
Server setup
TERMINAL
uvx a2a-mcp-serverMCP Clients
Claude Desktop
CLAUDE DESKTOP · JSON
{
"mcpServers": {
"a2a": {
"command": "uvx",
"args": [
"a2a-mcp-server"
]
}
}
}Cursor
Start the server with the streamable-http transport and leave it running
CURSOR · TERMINAL
MCP_TRANSPORT=streamable-http MCP_HOST=127.0.0.1 MCP_PORT=8000 uvx a2a-mcp-serverIn Cursor, go to Settings > AI > MCP Servers and add a server with this URL:
CURSOR · JSON
{
"mcpServers": {
"a2a-mcp-server": {
"url": "http://127.0.0.1:8000/mcp"
}
}
}
