Check an Aadhaar number's format

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

Annotations already declare readOnly, idempotent and closed-world, but the description goes well past them: nothing is stored, logged or looked up, and only the last 4 digits come back. That is exactly the privacy-relevant behavior an agent needs to know before sending a sensitive identifier, and it is information the annotations could not convey.

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?

Three short sentences, each doing distinct work: what is checked, what is not done with the input, and what the result does and does not prove. The scope restriction is front-loaded, and there is no filler.

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, no-output-schema validator, the description covers the input rules, the privacy behavior, and the return shape (last 4 digits plus a pass/fail semantics). Nothing an agent needs in order to call it correctly or interpret the answer is missing.

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%, so the baseline is 3. The description adds real meaning about what the parameter must contain (12 digits subject to a starting-digit rule and a Verhoeff checksum), while the schema supplies the 'spaces allowed' detail and length bounds; the two are complementary rather than redundant.

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 ('Checks only the FORMAT of an Aadhaar number') and enumerates the exact rules applied: 12 digits, not starting with 0 or 1, Verhoeff checksum. The word 'only' immediately separates it from any sibling that might look up or verify real numbers, so an agent can distinguish it from validate_gstin/validate_pan/lookup_pincode without opening any schema.

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 explicit negative guidance ('Do not use this to identify people') and a critical caveat that a pass does not mean the number was issued, which defines the boundary of what the result means. What it lacks is a positive framing of when to reach for this versus the other validate_* siblings, though the resource named in the description makes the split fairly obvious.

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