grpc_frame_build
Encode one or more messages into a gRPC / gRPC-Web length-prefixed body. Inverse of grpc_frame_parse — for constructing test or replay bodies. Each message takes payloadHex plus optional compressed / isTrailer flags.
This record as markdown: /tools/io-github-vmoranv-jshookmcp/grpc-frame-build.md
What grpc_frame_build does on Jshookmcp
AI agents invoke grpc_frame_build to trigger actions in Jshookmcp. 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.
Why grpc_frame_build is rated High
Constructs gRPC payloads for network transmission, enabling test replay or message injection attacks.
From the tool's definition Encode messages into gRPC body; constructing test or replay bodies
Attacks that exploit this kind of access
The rule that runs grpc_frame_build safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Jshookmcp, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For grpc_frame_build, this is the rule to start with:
grpc_frame_build 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.
The button opens the PolicyLayer dashboard: create your workspace, connect Jshookmcp, apply this rule, and every grpc_frame_build call is checked against it from then on.
Questions about grpc_frame_build
Encode one or more messages into a gRPC / gRPC-Web length-prefixed body. Inverse of grpc_frame_parse — for constructing test or replay bodies. Each message takes payloadHex plus optional compressed / isTrailer flags. It is categorised as a Execute tool in the Jshookmcp MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Jshook MCP server in PolicyLayer and add a rule for grpc_frame_build: 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 Jshookmcp. Nothing to install.
grpc_frame_build 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 grpc_frame_build 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 grpc_frame_build. 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.
grpc_frame_build is provided by the Jshook MCP server (@jshookmcp/jshook). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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