Send a follow-up message to an existing A2A task. Continues the conversation within the task context.
Part of the Agent0 server.
Free to start. No card required.
AI agents use a2a_task_message to create or modify resources in Agent0. Write operations carry medium risk because an autonomous agent could trigger bulk unintended modifications. Rate limits prevent a single agent session from making hundreds of changes in rapid succession. Argument validation ensures the agent passes expected values.
Without a policy, an AI agent could call a2a_task_message repeatedly, creating or modifying resources faster than any human could review. PolicyLayer's rate limiting ensures write operations happen at a controlled pace, and argument validation catches malformed or unexpected inputs before they reach Agent0.
Write tools can modify data. A rate limit prevents runaway bulk operations from AI agents.
{
"version": "1",
"default": "deny",
"tools": {
"a2a_task_message": {
"limits": [
{
"counter": "a2a_task_message_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}See the full Agent0 policy for all 34 tools.
These attack patterns abuse exactly the kind of access a2a_task_message gives an agent. Each links to the full case and the policy that stops it:
Other write tools across the catalogue. The same approach applies to each: rate-limit and validate the arguments.
Send a follow-up message to an existing A2A task. Continues the conversation within the task context.. It is categorised as a Write tool in the Agent0 MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Agent0 MCP server in PolicyLayer and add a rule for a2a_task_message: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Agent0. Nothing to install.
a2a_task_message is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the a2a_task_message rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for a2a_task_message. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
a2a_task_message is provided by the Agent0 MCP server (@rickydata/agent0-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 34 Agent0 tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
4,600+ MCP servers and 31,000+ tools scanned and risk-classified.