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

With no annotations supplied, the description carries the full disclosure burden and does so: it states the cost (€0.0005 per call) and the auth mechanism (Authorization: Bearer API key), that tokens and keys are never logged or cached, the 10-minute JWKS cache, and the security property that algorithm families are pinned to key type to block alg-confusion attacks. These are exactly the operational facts an agent cannot infer from the schema.

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?

Structure is front-loaded: operations and their key requirements come first, then security/cost properties, then the parameter glossary. It is dense with no filler, though the trailing parameter enumeration reads as one long run-on sentence rather than a scannable list.

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?

Given nine all-optional params, no annotations and an output schema that handles return values, the definition is nearly complete. The remaining gap is failure semantics: it does not say whether an invalid signature raises an error or returns a negative verdict, nor how malformed tokens are reported, which matters for an agent branching on the result.

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% and all nine params are bare titles, so the description must compensate and does: every parameter is annotated with its meaning and which op consumes it (token for decode/verify, secret for HMAC verify/sign, public_key for verify, private_key for sign, jwks_url for verify, payload as a JSON claims object, alg with allowed values and HS256 default, exp_seconds as lifetime). It even resolves the otherwise-ambiguous op default.

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 names three concrete operations (decode, verify, sign) on a specific resource (JWT) and states what each does: reading header/payload, checking a signature, or issuing a token. It also makes the decode-vs-verify distinction explicit ('without checking the signature'), which is the main ambiguity an agent could hit; no sibling tool overlaps this space.

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 per-operation selection guidance: use decode to inspect, verify to validate against a secret/PEM/JWKS, sign to mint a token, with op defaulting to decode. It does not state exclusions or point to any alternative tool (e.g. hash or base64 for adjacent tasks), so it stops short of full when/when-not routing.

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