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

With no annotations, the description carries the full burden but does disclose two important traits: it is a paid call ($0.10 via x402 on USDC Base) and it does not verify signatures, which is a consequential security limitation. It does not say what happens with a malformed or unsigned token, nor the response shape beyond the three named sections.

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?

A single dense line with no wasted clauses; cost, purpose, limitation, and argument are all packed in. The payment notice sitting ahead of the purpose is slightly awkward ordering but still readable.

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, no-output-schema tool, it covers the essentials an agent needs: price, semantics of the result (header/payload/expiry), and the non-verification caveat. Remaining gaps are the input format and error behavior, minor given the tool's simplicity.

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 0%, so the description must compensate, yet 'Args: token (string)' only repeats the schema's name and type. It omits the practically important detail of whether the value should be the raw JWT or include a 'Bearer ' prefix.

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 and resource ('JWT decoder') and enumerates exactly what it returns: header, payload, and expiry status. The explicit 'NO signature verification (inspection only)' boundary separates it from any verification-type tooling, so an agent can identify it immediately.

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?

'inspection only' plus 'NO signature verification' tells the agent the context in which this tool is appropriate — decoding/debugging a token, not establishing trust — which functions as an implicit when-not. It stops short of naming an alternative for signature verification or stating prerequisites other than payment.

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