Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations declare readOnlyHint=true and idempotentHint=true, but the description says each call costs $0.001 and that with a P0 key the tool 'makes the paid call itself' while 'deducting the listed price.' Charging is an environmental side effect and repeated calls incur repeated charges, so the description contradicts the read-only and idempotent annotations.

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 front-loads the usage condition and keeps the operational details together. It is somewhat dense and includes a full key-purchase URL, but the added length is largely justified by the dual-mode payment behavior.

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?

With no output schema, the description still explains the decoded return fields, the no-key request-descriptor behavior, the paid-call behavior with a P0 key, and that bad input is rejected before charging. That is sufficient for an agent to understand what comes back and what the call costs.

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 tool has one parameter, token, and schema description coverage is 100% with 'JWT header.payload.signature.' The description explains what is decoded from the token but adds no syntax or format detail beyond the schema, so the baseline of 3 applies.

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 states a specific verb and resource: inspect/decode a JWT without a key, returning header, payload, alg, kid, timestamps, and expiry status. This is clear enough to distinguish it from general utilities like util_base64 or util_hash.

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?

It explicitly says when to use the tool: when you need to inspect a JWT without a key. It also explains the two invocation modes, with an x402/MPP client or via a P0 access key, but it does not name alternatives or when-not-to-use conditions.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.