validate_din

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

Annotations already mark the tool as read-only and idempotent. The description adds valuable behavior beyond annotations: shorter inputs are zero-padded, spaces are stripped, and only format validation is performed, not director status verification. No contradiction with annotations.

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 compact and front-loaded with the core action and use case. The Args block is somewhat redundant with the schema, but every sentence still carries useful information and the total length is appropriate.

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?

This is a simple single-parameter validation tool with an output schema, so no hidden behavior remains. The description fully covers what is validated, input normalization, read-only nature, and the explicitly excluded status verification.

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?

Input schema has 100% coverage for the single parameter, which is the baseline. The description adds extra meaning by specifying that the 8-digit value is numeric, shorter values are zero-padded, and spaces are stripped—details absent from the schema.

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?

States a specific verb plus resource: 'Validate an Indian DIN (Director Identification Number) format'. This distinguishes it from sibling tools like validate_cin, validate_pan, or validate_aadhaar, and ties it to MCA compliance.

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?

Explicitly says when to use: 'Use when verifying director identity numbers in MCA compliance workflows.' It also clearly states a limitation ('Format validation only. Cannot verify director status with MCA'), but does not name an alternative tool for the more comprehensive verification.

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