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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, destructiveHint=false), and the description adds meaningful context beyond them: "No sign-in" (no auth required) and the explicit reassurance that this does not purchase the number. It doesn't mention rate limits or latency, but the key behavioral caveats are present.

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?

Purpose and result are front-loaded, and the pricing-model sentences all earn their place. The middle is somewhat dense and could be tightened, but 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?

With no output schema, the description correctly states what is returned (monthly amount, whether local calls are included), and it explains the channel-pack pricing needed to call the tool correctly. Remaining gaps are the undocumented country/number_type value formats.

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 only 50% (currency and channel_count documented; country and number_type bare), and the description meaningfully compensates for the hardest parameter by explaining the 2-included / 10-per-pack model and what channel_count actually computes for a target like 15. country and number_type formats/values remain unexplained, so it isn't fully compensating.

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?

States a specific verb (price/quote) and resource (a Widely phone number) plus what the result contains (monthly amount, local-call inclusion). This clearly separates it from quote_call, quote_esim, quote_port and quote_service, though it doesn't explicitly name those siblings or how it differs from get_did_rate.

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?

"Use this when a UK, US, Israeli, or other local number is needed" gives a clear when-to-use trigger, and "This does not purchase the number" sets an explicit boundary against acquisition. It stops short of naming the alternative quote/purchase tools to route to.

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