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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds genuinely non-obvious behavior: the x402 payment path, the two supported chains (Base or Solana), and the billing condition that charges apply only when records are found. It omits rate limits and any note on empty-result behavior, keeping it short of a 5.

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?

Two sentences, front-loaded with what is returned, then the payment mechanics. Nothing is redundant. The first sentence is a sentence fragment and the pricing sentence is dense, which slightly hurts readability but not efficiency.

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 read-only lookup with no output schema, the description covers what comes back ('data seen for each'), the cost model, and the payment fallback. It is nearly complete; only the shape of a 'record' and empty-result handling are left implicit.

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?

There is a single parameter and schema coverage is 100%, with the schema itself specifying 'digits only, country code first'. The description adds no formatting, normalization, or example detail beyond 'phone number', so baseline 3 applies.

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 names the resource (a phone number) and states the return content specifically: sites and accounts tied to the number plus the data seen for each. That is more informative than a generic 'look up a phone'. However, it never distinguishes itself from the sibling phone_lookup, so an agent cannot tell from the text which of the two phone tools to pick.

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 only implied through the pricing clause ('per search'), which signals a paid lookup operation but gives no explicit when-to-use condition and no mention of the obvious alternative, phone_lookup. The '$0.25 charged only when it finds records' line does give the agent a cost-based decision input, which lifts this above pure silence.

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