hash
Computes cryptographic digests and HMAC signatures. Returns hex and base64 at once, so a webhook signature can be compared in whichever encoding the provider uses. MD5 and CRC32 are included for checksums and legacy fixtures; they are not secure for authentication.
This record as markdown: /tools/com-fluentedi-tools/hash.md
What hash does on Tools
AI agents call hash to retrieve information from Tools without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
| Parameter | Type | Required | Description |
|---|---|---|---|
input | string | Yes | Text to hash. |
hmac_key | string | — | When set, computes HMAC-<algorithm> with this key instead of a plain digest. Not supported for md5/crc32. |
algorithms | array | — | Any of: md5, sha1, sha256, sha384, sha512, crc32. |
input_encoding | string | — | How to read `input` into bytes. |
Parameters from the server's own tool schema.
Why hash is rated Low
Even though hash only reads data, uncontrolled read access leaks sensitive information and racks up API costs: an agent caught in a retry loop can make thousands of calls a minute without anyone noticing.
Attacks that exploit this kind of access
The rule that runs hash safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Tools, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For hash, this is the rule to start with:
hash is read-only, so it stays allowed. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect Tools, apply this rule, and every hash call is checked against it from then on.
Questions about hash
Computes cryptographic digests and HMAC signatures. Returns hex and base64 at once, so a webhook signature can be compared in whichever encoding the provider uses. MD5 and CRC32 are included for checksums and legacy fixtures; they are not secure for authentication. It is categorised as a Read tool in the Tools MCP Server, which means it retrieves data without modifying state.
hash accepts 4 parameters: input, hmac_key, algorithms, input_encoding. Required: input. The full parameter table on this page comes from the server's own tool schema.
Register the Tools MCP server in PolicyLayer and add a rule for hash: 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 Tools. Nothing to install.
hash is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the hash 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 hash. 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.
hash is provided by the Tools MCP server (https://fluentedi.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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