Respond to a specific query
AI agents use respond_to_query to create or update resources in A2AMCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your A2AMCP environment.
This tool writes/posts a response back to a querying agent in the coordination system. It creates new message data in Redis but does not delete anything, execute code, or involve financial transactions. Misuse could disrupt inter-agent communication or inject misleading coordination data, hence medium severity.
From the tool's definition 'Respond to a specific query' — sends a response message to another agent
Documented attack patterns abuse exactly the kind of access respond_to_query gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and A2AMCP, and nothing reaches the server without passing your rules. This is the rule we recommend for respond_to_query:
{
"version": "1",
"default": "deny",
"tools": {
"respond_to_query": {
"limits": [
{
"counter": "respond_to_query_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}respond_to_query stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
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Respond to a specific query. It is categorised as a Write tool in the A2AMCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the A2A MCP server in PolicyLayer and add a rule for respond_to_query: 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 A2AMCP. Nothing to install.
respond_to_query 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 respond_to_query 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 respond_to_query. 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.
respond_to_query is provided by the A2A MCP server (webdevtodayjason/a2amcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from A2AMCP, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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17 A2AMCP tools catalogued and risk-classified — across an index of 43,000+ MCP servers.