lookup_hsn_code

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

With no annotations, the description carries the disclosure burden. It clearly states the output shape and proactively warns that the tool does not return a GST rate, explaining why. It doesn't cover invalid-code or not-found error behavior, but that is a minor gap for a simple lookup tool.

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?

Two sentences with no filler. The first sentence states the core return value, and the second delivers the critical caveat about GST rates. Every phrase earns its place.

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-parameter lookup with no output schema, the description gives the essential information: input type, returned fields, and the prominent non-goal. An agent has enough context to invoke it correctly and avoid the most likely misuse.

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 already documents code as a required 2-8 digit HSN/SAC string, so schema coverage is 100%. The description reinforces the same format but adds no substantial new parameter-level meaning beyond what the schema provides.

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 clearly specifies what the tool returns: the official description for a 2-8 digit HSN/SAC code plus the chapter/heading/subheading it belongs to. It also distinguishes itself from a search tool by being code-based, though it never explicitly names the sibling alternative.

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 intended use is clear: given a 2-8 digit HSN/SAC code, retrieve the official description and taxonomy position. It also provides an explicit when-not by warning that no GST rate is returned, though it does not name alternatives like search_hsn_codes.

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