AI agents invoke string_increment_float to trigger actions in AWS AppSync MCP Server. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.
The description is minimal and uninformative. 'Increment float value' suggests modifying/updating a numeric value, which could be a Write operation. However, given the AWS AppSync context (a GraphQL service), this likely triggers a resolver or operation against a data source. The vague description lowers confidence significantly.
From the tool's definition 'Increment float value' - the tool modifies a numeric value in some data store or context
Documented attack patterns abuse exactly the kind of access string_increment_float gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and AWS AppSync MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for string_increment_float:
{
"version": "1",
"default": "deny",
"tools": {
"string_increment_float": {
"limits": [
{
"counter": "string_increment_float_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}string_increment_float stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.
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Increment float value. It is categorised as a Execute tool in the AWS AppSync MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the AWS AppSync MCP Server MCP server in PolicyLayer and add a rule for string_increment_float: 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 AWS AppSync MCP Server. Nothing to install.
string_increment_float is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the string_increment_float 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 string_increment_float. 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.
string_increment_float is provided by the AWS AppSync MCP Server MCP server (awslabs.aws-appsync-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from AWS AppSync MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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805 AWS AppSync MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.