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

With no annotations provided, the description carries the full behavioral burden. It discloses two important traits: decoding occurs 'without verification' and invoking the tool 'Costs $0.001 USDC on Base via x402.' It does not cover malformed-token handling, return format, or security limitations beyond lack of signature verification.

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 two sentences, front-loads the core action and non-verification behavior, then appends payment cost. Every sentence adds relevant information with 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?

For a simple JWT decoder with one input parameter, no annotations, and no output schema, the description provides the critical caveat that it does not verify signatures and notes the payment requirement. It is mostly complete, though it could clarify the return shape or error behavior for invalid tokens.

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. It clarifies that the input is a JWT by saying 'Decode JWT header and payload,' but it does not specify the expected token format, such as compact serialization with dot-separated segments. The single parameter is obvious from context but remains under-documented.

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: 'Decode JWT header and payload.' It also distinguishes the behavior from verification, which is the closest sibling capability, so an agent can tell what this tool does 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?

It gives clear usage contexts: 'for inspection, debugging and agent workflows.' It also notes the tool operates 'without verification,' which implicitly tells the agent when to use it. However, it does not explicitly name an alternative tool for verification or state when not to use this decoder.

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