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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description still adds real value beyond that: it discloses a key limitation (no verification against the tax department) and a privacy property ("Nothing is stored"), plus that the result includes decoded holder type. Only the exact success/failure output shape is left unstated.

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, front-loaded with the core action, followed by scope limitation and privacy note. Nothing is padded and each sentence adds a distinct fact.

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 one-parameter, non-destructive validator with no output schema, the description covers purpose, limits, privacy and part of the return content (holder type). The only meaningful gap is the accepted input format and the exact validity response, which the agent must infer.

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 0% for the single required "pan" parameter, so the description must carry the meaning. It identifies the value as an Indian PAN, which is genuinely informative, but never states the expected format (10-character alphanumeric pattern) or whether input should be normalized/uppercased, leaving the agent to guess.

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 ("Validate an Indian PAN") and immediately scopes what validation means: format checking plus decoding of holder type (individual, company, firm and others). That distinguishes it from the many other validate_* siblings (validate_gstin, validate_iban, validate_vin) without needing the 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?

Usage is implied rather than stated: the agent learns the tool checks format only and explicitly not the tax department, which is a useful boundary. However, no alternative is named (e.g. pointing to validate_gstin for GST numbers) and there is no explicit "use this when..." framing.

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