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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so safety is covered. The description adds genuinely non-redundant behavior: results are computed at fixed 100/200 calls-per-month tiers and the data comes from scraped vendor pages via a named source, which tells the agent the numbers are derived and third-party in origin.

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 core operation and volume tiers before the attribute list, with the data-source note trailing as provenance. The attribute enumeration is dense but earns its place by previewing the comparison output; only the URL is arguably optional.

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 usefully enumerates what comes back (cost, billing model, plan limit, contract, trial, spam billing, integrations, score) and fixes the volume assumptions that shape those figures. Combined with the 100% schema coverage and full read-only annotations, an agent has everything needed to call and interpret it.

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% and the single parameter already documents 'Vendor ids or names', which the description repeats almost verbatim. The only mild addition is echoing the minItems=2 constraint as 'two or more'; the maxItems=6 cap is not mentioned. Baseline 3 is appropriate.

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 operation (side-by-side comparison) on a specific resource (AI receptionists) and enumerates the exact dimensions compared at two fixed volume tiers. This clearly distinguishes it from the singular get_vendor and from the ranking-oriented siblings get_rankings/list_rankings.

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?

'Two or more' plus 'side by side' implies the multi-vendor use case that separates it from get_vendor, but no sibling is named and no exclusion is stated. There is no explicit guidance on when to prefer this over fetching vendors individually or over the rankings tools.

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