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

Annotations already declare readOnlyHint, idempotentHint, and closed-world behavior. What the description adds is valuable: the content of the result (what's free, limits, catches, how to start, checked dates) and the presence of a side-by-side table link, which matters since there is no output schema. It stops short of stating behavior on invalid tool names or how results are ordered.

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?

Two tightly packed sentences, front-loaded with the comparison payload before the secondary link explanation. Slight redundancy in describing both the side-by-side table link and the per-tool page link, but nothing is wasted.

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 reasonably well by enumerating the fields returned. Remaining gaps are error behavior and result structure, minor for a one-parameter read-only tool.

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 is already described as 'Tool names or websites to compare.' The description restates the 2-to-4 cardinality but adds no new meaning about accepted name formats, ambiguity handling, or matching behavior, so baseline 3 applies.

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 and resource (compare free plans) plus a scope constraint (2 to 4 AI tools side by side), which implicitly separates it from the single-tool sibling check_free_plan. It never names that sibling, so the differentiation is inferential rather than explicit.

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 implied by the '2 to 4 tools side by side' phrasing, which suggests the multi-tool case, but there is no explicit when-to-use statement, no exclusion pointing to check_free_plan for a single tool, and no prerequisite guidance.

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