hmac
HMAC Generator — Compute an HMAC digest (SHA-256 by default) for a key–message pair.
This record as markdown: /tools/com-wingmanprotocol-agent-gateway/hmac.md
What hmac does on Gateway
AI agents invoke hmac to trigger actions in Gateway. 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.
| Parameter | Type | Required | Description |
|---|---|---|---|
key | string | Yes | Secret key |
message | string | Yes | Message to authenticate |
algorithm | string | — | Hash |
Parameters from the server's own tool schema.
Why hmac is rated High
The tool performs a cryptographic computation (HMAC generation) given inputs. It executes a deterministic algorithm rather than reading stored data or writing/modifying any state. No destructive or financial effects are possible. Severity is low because it is a pure cryptographic utility with no side effects, but it does process potentially sensitive key material.
From the tool's definition Compute an HMAC digest (SHA-256 by default) for a key–message pair
Attacks that exploit this kind of access
The rule that runs hmac safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Gateway, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For hmac, this is the rule to start with:
hmac 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 Gateway, apply this rule, and every hmac call is checked against it from then on.
Questions about hmac
HMAC Generator — Compute an HMAC digest (SHA-256 by default) for a key–message pair. It is categorised as a Execute tool in the Gateway MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
hmac accepts 3 parameters: key, message, algorithm. Required: key, message. The full parameter table on this page comes from the server's own tool schema.
Register the Gateway MCP server in PolicyLayer and add a rule for hmac: 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 Gateway. Nothing to install.
hmac 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 hmac 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 hmac. 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.
hmac is provided by the Gateway MCP server (https://wingmanprotocol.com/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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