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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is fully covered. The description adds real value beyond that by disclosing the data source ('catalog data', i.e. cached rather than live) and enumerating the comparison dimensions, which partially substitutes for the missing output schema.

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 is front-loaded in the first clause, but the rest is a single run-on sentence listing roughly eighteen comma-separated attributes of varying importance. It earns its place content-wise yet is hard to scan; grouping or prioritization would improve parseability.

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 burden of explaining the return content, and it does so thoroughly, including the 'who wins on each' verdict. The only meaningful gap is that no alternative tools or use-case conditions are mentioned, which is captured under usage guidelines rather than completeness.

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 description coverage is 100%, with host_a/host_b accepting slug, domain, or exact name and locale explicitly mapping to currency. The description adds nothing about the parameters themselves, so the baseline 3 applies; the RAM-tier list refers to output content, not 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?

States a specific verb (compare), an exact scope ('two VPS hosts'), and enumerates precisely what is compared (cheapest plan per RAM tier, median price, NVMe share, SLA, 'who wins on each'). An agent can immediately tell this apart from single-host lookups like get_vps_host or filtered lists like search_vps without opening any schema.

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?

No statement of when to use this versus get_vps_host, search_vps, or vps_rating, and no prerequisites or exclusions. The only contextual cue is 'from catalog data', which hints at data provenance rather than selection guidance. The agent must infer that it should call this only when comparing exactly two known hosts.

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