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

The description discloses the single most important behavioral trait beyond the annotations: the signature is NOT verified, so the output is untrusted inspection data. It also states it reports expiry status and the exact expiry date, giving the agent concrete output expectations. The annotations cover safety (readOnly, non-destructive), so this addition is exactly the value-add layer.

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 tight sentences: the first defines the operation and its semantics, the second gives usage context. No redundant restatement of the name or 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?

With an output schema present and full parameter coverage, the description need only convey purpose, the no-verification caveat, and when to reach for it — all of which it does. Nothing required to call this 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?

There is one required parameter at 100% schema coverage, with the schema documenting the 'header.payload.signature' format. The description adds no format or syntax detail beyond that, so it neither compensates nor detracts — the baseline 3 applies.

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 ('Decode a JWT') plus the exact return content (header and payload) and a key scoping caveat ('without verifying the signature'). This clearly separates it from siblings like base64_decode or extract_json_path, which handle unrelated formats.

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?

Explicitly names the use case — inspecting claims (sub, iss, exp, roles) during debugging or auth-provider integration — which tells the agent when this is the right tool. It does not, however, name an alternative for validation/verification scenarios, so the agent must infer that no sibling verifies signatures.

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