jwt_decode
JWT Decoder (no signature verification) — Decode a JWT's header and payload to JSON. Does NOT verify the signature — contents are unauthenticated.
This record as markdown: /tools/com-wingmanprotocol-agent-gateway/jwt-decode.md
What jwt_decode does on Gateway
AI agents call jwt_decode to retrieve information from Gateway 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 |
|---|---|---|---|
token | string | Yes | The JWT (two or three dot-separated segments) |
now_epoch | number | — | Optional Unix seconds to check exp/nbf against (never the wall clock) |
Parameters from the server's own tool schema.
Why jwt_decode is rated Low
This tool extracts and parses data from a JWT token without side effects. It reads/queries the JWT structure but does not modify, delete, or execute operations. The severity is medium (not low) because JWT payloads often contain sensitive claims (user IDs, permissions, PII) that could enable further attacks if an agent misuses decoded tokens, though the tool itself only retrieves information.
From the tool's definition Tool name is 'jwt_decode' and description states it 'Decode[s] a JWT's header and payload to JSON'. The verb 'decode' and 'to JSON' indicate retrieval/parsing of data.
Risk signalsHandles credentials or secrets (token)
Attacks that exploit this kind of access
The rule that runs jwt_decode 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 jwt_decode, this is the rule to start with:
jwt_decode 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 Gateway, apply this rule, and every jwt_decode call is checked against it from then on.
Questions about jwt_decode
JWT Decoder (no signature verification) — Decode a JWT's header and payload to JSON. Does NOT verify the signature — contents are unauthenticated. It is categorised as a Read tool in the Gateway MCP Server, which means it retrieves data without modifying state.
jwt_decode accepts 2 parameters: token, now_epoch. Required: token. 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 jwt_decode: 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.
jwt_decode 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 jwt_decode 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 jwt_decode. 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.
jwt_decode 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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