Decode a JWT token to inspect header and payload claims without signature verification, enabling quick debugging of authentication and authorization data.
Decode a JWT token to inspect header and payload claims (does NOT verify signature).
| Name | Required | Description | Default |
|---|---|---|---|
| token | Yes | JWT token string. |
Changes observed during successful MCP inspections.
v0.1.11Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full burden, and it discharges the most important obligation by explicitly stating the signature is NOT verified — a security-relevant fact the agent must know. It stops short of describing malformed-token behavior or failure modes, so it is strong but not complete.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
One sentence, front-loaded with the action and resource, with the critical caveat bracketed at the end. Zero waste and nothing important buried.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a one-parameter, side-effect-free decode tool with no output schema, the description tells the agent what it gets (header and payload claims) and the key limitation. Only minor gaps remain: no note on error behavior for invalid tokens and no explicit warning about trusting unverified claims.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
There is a single parameter and schema description coverage is 100%, so the schema already documents the 'token' string. The description adds no format guidance (e.g., whether the 'Bearer ' prefix is accepted), which is the baseline expectation when the schema does the heavy lifting.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
States a specific verb (decode) and resource (JWT token) plus the exact artifacts produced (header and payload claims). The parenthetical negative scope ('does NOT verify signature') further sharpens what the tool is and is not, so an agent can distinguish it from any verify-style sibling at a glance.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
Usage is implied by the stated purpose — use it to inspect a token's contents — and the non-verification caveat hints at the boundary condition. However, it never says when to prefer this over alternatives (e.g., a verifying introspection tool) or that unverified claims must not be trusted for authorization decisions.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.