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

Annotations already establish readOnly/idempotent/non-destructive/openWorld=false, so the remaining burden is light. The description adds real value beyond them: the pricing basis (3-minute calls), the data source and check date (provenance and freshness), and the exact set of figures returned.

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?

Front-loaded with the returned figures, no filler sentences, and the source citation is short and justified by provenance needs. The first sentence is a dense four-item list that takes a second read, which keeps it from a 5.

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?

With no output schema, the description carries the return-value burden and does so by enumerating range, median, per-minute all-in rate, and entry-plan range. Minor gaps remain: no statement of currency, units, or response shape, and 'prices checked October 26, 2026' is a future date that an agent may find ambiguous.

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 baseline is 3, and the description earns one extra point by disclosing the measurement assumption behind `calls` (3-minute call duration), which the schema does not state. It also glosses `virtual` as live people, matching the enum description.

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?

Names the resource precisely (range and median monthly cost, all-in per-minute rate, entry-plan range) and scopes it to a category (AI vs live virtual receptionists) at a given call volume. An agent can distinguish this aggregate category view from get_vendor_pricing and compare_at_volume by inference, but the description never names those siblings explicitly.

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: the word 'category' and the aggregate framing suggest this is the tool for a benchmark/summary rather than per-vendor detail, but there is no explicit when-to-use, when-not-to-use, or named alternative among compare_at_volume, get_vendor_pricing, or hire_vs_ai.

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