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

With no annotations supplied, the description carries the full burden and does reasonably well: it discloses that the signature is NOT verified (a security-relevant caveat), that the operation is pure CPU and instant, and that expiry/TTL are computed. It omits what happens on malformed or non-JWT input, which is the remaining behavioral 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?

Three short clauses, front-loaded with the action and its most important caveat. 'Pure CPU, instant' is terse and useful; nothing is redundant or padded.

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 the description covers what goes in, what comes out (header, payload, expiry, TTL), and the verification caveat, which is enough to call it correctly. Only the malformed-input behavior is left unaddressed.

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 a single required 'token' parameter with 100% schema description coverage, so the schema already documents it fully. The description adds no format or encoding hints (e.g., compact serialization, bearer prefix handling) beyond the schema, which is the baseline for full coverage.

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 into its header and payload') plus a key scope qualifier ('without verifying the signature'). It does not distinguish itself from the sibling decode_jwt, and token_verdict may overlap on claims/expiry territory, so an agent cannot tell these apart from the description alone.

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?

'Use to inspect a token's claims' gives an implied usage context, but there is no when-not guidance and no mention of the obvious alternative decode_jwt or token_verdict. Usage is inferable but not routed.

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