Decode a JWT header+payload with safety flags (never verifies the signature) Free check: https://sigtap-outreach-api.sigtap.workers.dev/preview/tools/jwt-decode = 200 demo sample, no wallet. Paid call: 402 challenge -> sign -> retry = settled on-chain. ($0.001 USDC on Base, x402)
| Name | Required | Description | Default |
|---|---|---|---|
| token | Yes | JWT to decode |
| Name | Required | Description | Default |
|---|---|---|---|
| alg | Yes | ||
| flags | No | ||
| header | Yes | ||
| payload | Yes | ||
| signature | No |
Changes observed during successful MCP inspections.
Output schema / (root)Previous value: -nullNew value: +{
+ "properties": {
+ "alg": {
+ "type": "string"
+ },
+ "flags": {
+ "type": "object"
+ },
+ "header": {
+ "type": "object"
+ },
+ "payload": {
+ "type": "object"
+ },
+ "signature": {
+ "type": "object"
+ }
+ },
+ "required": [
+ "header",
+ "payload",
+ "alg"
+ ],
+ "type": "object"
+}Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The description discloses that the tool does not verify signatures, a key behavioral trait. It also hints at a paid flow with a 402 challenge, implying a payment side effect. However, it does not explicitly state whether the tool is read-only, stores data, or requires special permissions, leaving some transparency gaps.
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?
The description is moderately concise, but includes extra details about free/paid calls, URL, and pricing that are not strictly necessary for understanding the core functionality. These could be moved to separate documentation, making the description more focused.
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?
The description lacks essential context about the 'safety flags' mentioned, and does not explain what the output format looks like. Given that the tool has an output schema (as suggested by context), the description should at least hint at the return structure. The payment flow is briefly mentioned but not fully described, leaving gaps for an agent.
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?
The sole parameter 'token' is described in the schema as 'JWT to decode'. The tool description adds clarity by specifying that it decodes the header and payload, which goes slightly beyond the schema. No format or constraints are provided, but the meaning is clear.
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?
The description clearly states the tool decodes a JWT header and payload, using the specific verb 'decode' and identifying the resource. However, the phrase 'with safety flags' is ambiguous and could confuse agents about the exact purpose or output.
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?
The description provides a caveat that it never verifies the signature, which implicitly advises against using it for verification. However, it does not explicitly state when to use this tool over siblings, nor does it compare alternatives. The free/paid distinction is about cost, not usage conditions.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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