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

With no annotations provided, the description carries the disclosure burden, and it delivers the most important safety fact: the token is decoded without signature verification, so results are untrusted. It also signals the return shape (header, algorithm, claims, timestamps, expiry). It omits error behavior for malformed or non-JWT input and any rate-limit/auth context, keeping it below a 5.

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?

Two compact sentences, front-loaded with the action and the non-verification caveat, then the enumeration of decoded fields, then the use case. No filler, no repetition of the title.

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 decode tool with an output schema, the description covers purpose, the key behavioral caveat, and enough about return content. Minor gaps remain around malformed-token behavior, which the output schema does not resolve since it describes success shape only.

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 coverage is 0%, so the description must compensate for the undocumented 'token' parameter. The phrase 'a JSON Web Token' implies the input is the raw token string, but no format guidance (e.g., compact dot-separated form, 'Bearer ' prefix handling) is given, so the added meaning is only partial.

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 (JSON Web Token), then enumerates what is extracted: header, algorithm, payload claims, issued-at/expiry, and expiry status. The phrase 'without verifying it' immediately distinguishes it from any verification-style capability, so an agent can identify its role without opening the schema.

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?

'Use to debug auth tokens and API sessions' gives a clear triggering context for the tool. It does not name exclusions or a concrete alternative (e.g., when to prefer a verification tool or decode_calldata), so it stops short of explicit when-not guidance.

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