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

Annotations already cover the read-only safety profile, and the description adds meaningful context beyond them: the signature is not verified (a critical caveat), plus cost ($0.001 via x402) and a rate limit (5 free calls/day). It stops short of describing error/malformed-token behavior.

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?

Front-loaded with the action and returned fields, followed by the key caveat and pricing. Three tight clauses, no filler.

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 fully explains what is returned and adds the non-verification caveat and cost model. Nothing an agent needs to invoke and interpret the call correctly is missing.

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?

Schema description coverage is 100%, and the schema itself documents the single 'token' parameter including the optional 'Bearer ' prefix. The description adds no parameter detail, so the baseline 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 (Decode) and resource (JWT) and enumerates the returned content: header, payload, issued/expiry times, and expiry status. jwt_decode is self-evidently distinct from the encoding/hashing siblings (base64, hash), so no confusion arises.

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 gives a clear usage boundary with 'Does not verify the signature,' which tells the agent when this tool is and isn't sufficient (e.g., not for trust/validation decisions). It does not name alternatives, but no sibling competes for this task.

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