jwt_decode

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

Discloses splitting on '.', base64url-decoding, JSON-parsing, no network calls, no key lookup, returns error on malformed input. No annotations provided, so description fully covers behavioral traits.

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?

Five focused sentences with no redundancy. Front-loaded with main purpose; each sentence adds value.

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-param tool with no output schema, description fully covers purpose, usage, behavior, and output format (header, payload, signature fields).

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% but description adds meaning: explains token format (three segments separated by dots) and requirement to remove Bearer prefix, which are not in schema.

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?

Clearly states it decodes JWT into header, payload, raw signature without verification. Distinguishes from sibling base64_decode by specifying JWT-specific behavior.

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 says to use for inspecting claims or debugging auth flows, and warns not to use decoded claims for access-control decisions because signature is not validated.

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