State and union territory codes

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

Annotations already establish readOnly, idempotent and closed-world, so the safety profile is covered. The description adds genuinely useful behavior that annotations cannot convey: the exact return payload (GST code, RTO prefixes, capital, QRMP GSTR-3B due day group) and the 'no query returns all 36' default. It stops short of saying how an unmatched query is handled or whether the result is a single record or a list when a partial name matches several states.

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: accepted inputs first, returned fields second, the list-all default front-loaded at the end where it is immediately actionable. Examples are embedded inline rather than given their own clauses.

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?

A one-parameter, optional-parameter lookup with full schema coverage has modest requirements, and the description fills them by naming the returned fields in lieu of an output schema and stating the empty-query behavior. Nothing an agent needs in order to call it correctly appears to be absent.

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%, and the schema's own description already says 'A name, GST code, ISO code or RTO prefix. Leave out to list all.' The prose restates that almost verbatim with illustrative values, adding only marginal meaning beyond the structured field, so the baseline of 3 applies.

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 opens with a specific verb and resource ('Looks up an Indian state or union territory') and enumerates the four accepted identifier types with concrete examples (27, IN-MH, MH). It is clearly a static reference lookup, which distinguishes it from the sibling tools, all of which validate or compute against inputs rather than resolve a code.

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 invocation contexts: supply any of four identifier forms, or omit the query to enumerate all 36. What is missing is any exclusion or error guidance, such as what happens on a misspelled name or an out-of-range code, and it does not explicitly redirect to a sibling for adjacent needs.

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