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

With no annotations, the description carries the full burden and does disclose the single most important behavioral trait: it does not verify signatures. It also states the returned fields (header, payload, expiry). It omits what happens on malformed or non-JWT input, which would be the remaining gap.

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 front-loaded sentence with the operation first and the safety caveat immediately after. No filler, no restatement 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 read tool with no output schema, the description covers the return shape (header + payload + expiry status) and the verification caveat. Error behavior on invalid tokens is the one missing piece an agent might want.

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?

Only one parameter at 100% schema coverage, and the schema already documents it as 'the JWT (3 dot-separated parts)'. The description adds no format or syntax detail beyond that, so this sits at the schema-backed baseline.

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?

Specific verb 'Decode' tied to a specific resource 'JWT header + payload', plus a stated scope limit (no signature verification) and an output facet (expiry status). It is clearly distinct from siblings like base64_decode or json_format, though it never names them.

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?

'No signature verification' implicitly signals the trust/inspection use case, but there is no explicit when-to-use statement, no guidance on when to prefer base64_decode or a verifying alternative, and no prerequisite or error-case notes.

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