decode_jwt
Decode a JWT token into its header, payload, and signature parts. Use this to inspect JWT tokens without verifying signatures. Returns the header (alg, typ) and payload (claims) decoded from base64. Parameters: token — The full JWT token string (3 dot-separated base64 parts).
This record as markdown: /tools/com-gadgethumans-swarm-x402-middleware/decode-jwt.md
What decode_jwt does on X402 Middleware
AI agents call decode_jwt to retrieve information from X402 Middleware 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 |
Parameters from the server's own tool schema.
Why decode_jwt is rated Low
The tool performs cryptographic decoding and inspection of JWT tokens, which is a read-only operation. It extracts and returns the constituent parts of a JWT (header, payload, signature) without modifying data, executing code, making financial transactions, or destructively deleting anything. The 'without verifying signatures' phrase confirms it performs inspection only, not validation or state changes.
From the tool's definition Tool description states 'Decode a JWT token into its header, payload, and signature parts' and 'inspect JWT tokens without verifying signatures.' These are query/retrieval operations that decode and return data with no side effects.
Risk signalsHandles credentials or secrets (token)
Attacks that exploit this kind of access
The rule that runs decode_jwt safely
PolicyLayer is an MCP gateway: it sits between your AI agents and X402 Middleware, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For decode_jwt, this is the rule to start with:
decode_jwt 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 X402 Middleware, apply this rule, and every decode_jwt call is checked against it from then on.
Questions about decode_jwt
Decode a JWT token into its header, payload, and signature parts. Use this to inspect JWT tokens without verifying signatures. Returns the header (alg, typ) and payload (claims) decoded from base64. Parameters: token — The full JWT token string (3 dot-separated base64 parts). It is categorised as a Read tool in the X402 Middleware MCP Server, which means it retrieves data without modifying state.
decode_jwt accepts 1 parameter: token. Required: token. The full parameter table on this page comes from the server's own tool schema.
Register the X402 Middleware MCP server in PolicyLayer and add a rule for decode_jwt: 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 X402 Middleware. Nothing to install.
decode_jwt 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 decode_jwt 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 decode_jwt. 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.
decode_jwt is provided by the X402 Middleware MCP server (@gadgethumans/x402). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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