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

With no annotations provided, the description must disclose behavioral traits on its own. It does mention the most important limitation (no signature verification) and implies it decodes both header and payload. However, it does not disclose error behavior for invalid tokens, whether it validates the token structure, or any other constraints. The description covers the primary caveat but leaves other potential behaviors undocumented.

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?

The description is a single sentence that front-loads the action and includes the essential caveat. Every word earns its place; there is no fluff or redundant information. It is concise while conveying the core functionality and a critical limitation.

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 the simplicity of the tool (one parameter, no nested objects) and the presence of an output schema (which likely details the return structure), the description covers the essential aspects. It explains what the tool does and its main limitation. It could add more about error handling or token validation, but for a simple decode operation, it is reasonably complete. The output schema likely fills in the return details.

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?

The input schema has zero description coverage, so the tool description must compensate. The description implies that the 'token' parameter is a JWT string, but it doesn't explicitly state the parameter's meaning or format. The single parameter is self-explanatory given the purpose, but the description adds minimal semantic value beyond the schema's type declaration.

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 states a specific action (decode) on a specific resource (JWT header+payload) and adds a critical caveat (no signature verification). It clearly distinguishes this tool from the other encoding/decoding siblings like base64_decode or url_decode, which target different formats. The verb and resource are unambiguous.

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?

The description implicitly communicates when to use this tool: when you have a JWT and need to inspect its header and payload without verifying the signature. The caveat 'no signature verification' tells the agent this is not for validation tasks, though it doesn't name alternatives explicitly. The usage context is clear enough for an agent to decide.

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