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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds no behavioral context beyond the annotations — no statement of what invoking it returns or whether it differs from simply reading a static constant. For a zero-param tool with annotations plus an output schema, the description contributes almost nothing new.

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 short sentence with no filler, and the key identifying information is front-loaded. It loses a point only because the sentence is framed as a description of a phone number rather than of the tool's behavior, so its brevity comes at the cost of clarity.

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?

The tool is simple: zero parameters and an output schema, so return values need not be explained. However, the description leaves the core question unresolved — what happens when the agent invokes it — which is the one thing the schema and annotations cannot answer. For a trivially simple tool this is adequate but not complete.

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 tool takes zero parameters, so there is no parameter semantics to explain; the baseline of 4 applies. Nothing in the description misleads about inputs.

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 a resource ('the number humans can call to reach the Privi voice agent') but never states the action the tool performs — it reads like documentation of a phone number rather than a callable operation. An agent can infer it returns a phone number, but must guess whether it dials, returns contact info, or something else. The parenthetical (pilots, pricing, founder) hints at routing but does not distinguish it from siblings like call_directory.

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?

There is no explicit when-to-use or when-not-to-use guidance. The phrase 'humans can call' weakly implies this is a number to hand to a human rather than something to invoke for agent-to-agent work, but that is inference, not guidance. No alternatives among the nine call_* siblings are named.

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