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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds genuine value beyond them by disclosing that the comparison-page URL is conditional ('when that pair has a public comparison page') and that the tool never creates comparisons, i.e. it only surfaces existing site data. It does not say what the response contains when no public page exists, which keeps it from a 5.

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 sentences with zero filler: the first front-loads what is returned, the second qualifies the one conditional behavior. Every clause carries information an agent cannot get from the schema alone.

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 enumerates the returned fields and the optional comparison URL, so an agent can predict the response shape. Gaps are minor: the effect of the locale parameter on returned names and URLs is left to the schema, and error behavior for unknown slugs is unstated.

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% and both parameters are documented with enum values and a default, so the schema does the heavy lifting. The description reinforces the slugs cardinality ('2 or 3 tools') consistent with minItems/maxItems, but adds nothing about the locale parameter or slug format beyond the schema.

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?

The description names a specific resource (side-by-side data for 2 or 3 tools) and enumerates the returned fields (pricing, categories, pros and cons, rating, website), which implicitly separates it from the single-tool sibling get_tool. It stops short of explicitly naming an alternative, so it is clear but not maximally differentiating.

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 context is only implied: the '2 or 3 tools' framing tells the agent to pick this over a single-tool call, and 'this tool never creates comparisons' rules out a write/creation expectation. There is no explicit when-to-use statement, no mention of the locale parameter's purpose, and no guidance on what to do when a requested tool slug does not exist.

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