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

With no annotations provided, the description carries the full burden. It discloses the core behavior (validation and enrichment) and the returned data categories, but it does not clarify side effects, read-only status, failure behavior, or data freshness. The behavior is not contradictory, just under-specified.

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?

A single compact sentence front-loads the action and then lists the enriched attributes. Every word contributes information; there is no filler or redundancy.

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 tool with no output schema, the description does enough by stating the input scope, the validation action, and the key output fields. It falls short only in not explicitly routing non-US phone numbers to the likely sibling run_phone_enrichment and not indicating behavior on invalid numbers.

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?

The schema already covers the only parameter fully, including format and example, so the description adds no new parameter-level meaning. The description's mention of enrichment fields provides broader output context, but the parameter semantics themselves come 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?

The description uses a specific verb ('Validates and enriches') with a clear resource ('a US phone number') and enumerates the output categories. The US qualifier distinguishes it from the sibling run_phone_enrichment tool without needing to open either 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?

The scope 'US phone number' implies when this tool should be used, but it does not explicitly state when to prefer run_phone_enrichment_us over run_phone_enrichment or any other sibling. There is no when-not-to-use guidance or mention of alternatives.

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