Decode JWT

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

Beyond the readOnlyHint and idempotentHint annotations, the description discloses the critical limitation that signature verification is not performed, and the output should not be considered authenticated. This is essential behavioral context that annotations do not provide, and it directly addresses a common failure mode of LLMs.

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?

Three sentences, zero filler. The core purpose is front-loaded, the critical caveat follows immediately, and the web link is a useful addition. Every sentence earns its place.

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 single-parameter read-only tool with full schema coverage and strong annotations, the description covers purpose, behavior, and safety caveats. It even includes a web version link. Nothing an agent needs to call it 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 coverage is 100%, so the schema already fully documents the token parameter. The description does not add parameter-specific details beyond what the schema provides (e.g., the optional 'Bearer ' prefix is already in the schema). It adds context about what the tool does with the token, but that is more about purpose than parameter semantics, so a baseline 3 is appropriate.

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 a JSON Web Token's header and payload') and distinguishes it from sibling decoding tools (base64, url) by focusing on JWT structure and expiry reporting. It is immediately clear what the tool does.

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?

The description explicitly warns that this tool only decodes and does not verify signatures, instructing never to treat contents as trusted. It also notes the model's tendency to invent claims, which implicitly tells when to rely on this tool. No alternative is named, but no sibling offers JWT verification, so usage is clear.

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