Look up an Indian pincode

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

The annotations already declare readOnlyHint, idempotentHint, and openWorldHint=false. The description adds meaningful context beyond that: it identifies the bundled India Post directory and warns that dated data means newer pincodes will not be found. It does not describe error behavior for malformed input, but the key data-source limitation is disclosed.

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 two sentences, front-loaded with what is returned and followed by the important staleness caveat. Every sentence earns its place with no unnecessary wording.

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 simple one-parameter read tool with no output schema, the description enumerates the returned fields and explains the source and date limitation. It is nearly complete, though it could explicitly state what happens for an invalid or not-found pincode.

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 description coverage is 100%, and the schema already documents the single pincode parameter as a 6-digit value. The description repeats the 6-digit requirement but adds no additional syntax or format meaning beyond what the schema provides, so this is the baseline score.

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 verb and resource: it returns state, district, postal circle, and post offices for a 6-digit Indian pincode. This clearly distinguishes it from sibling validators such as validate_gstin and validate_pan, which check formats rather than look up directory data.

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 gives a clear lookup context and adds a useful staleness caveat about pincodes created after the directory date. However, it does not explicitly name alternatives or state when not to use this tool versus sibling tools like state_info.

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