Validate GSTIN

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

The description discloses critical behavioral traits beyond the annotations, specifically that the tool 'works offline.' This operational constraint is highly valuable context for an agent planning its execution environment.

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 definition is highly concise, using only two sentences to cover the function, the scope of the checks, and the operational constraints. The information is front-loaded and structured logically.

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 that the tool is relatively simple (one parameter) and highly constrained by its offline nature, the description is exceptionally complete. It covers functionality, scope, and limitations without requiring the agent to infer behavior.

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?

While the input schema is very clear (100% coverage), the description adds crucial semantic context by specifying that the input must be an 'Indian GSTIN' and defining what types of checks are performed (format, state code, and checksum). This clarifies the domain scope of the tool.

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 explicitly states the tool's purpose: to 'Check whether an Indian GSTIN is valid' and 'decode its state, PAN and entity type.' This is a clear and specific function that immediately differentiates it from other lookup or calculation tools in the sibling list.

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 provides a vital usage limitation, stating that while it validates the format, it 'does not confirm the registration is active on the GST portal.' This gives the agent a clear boundary for when the tool's output should be trusted.

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