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

Annotations already declare a safe, read-only, idempotent, closed-world read. Beyond that, the description discloses what the output actually contains: prices verified on the competitor's own pages, a vendor disclosure, and a conditional price-beat offer, plus that results may favor the competitor. That is meaningful behavioral context an agent cannot get from the annotations.

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, followed by the fallback behavior. The middle sentence is dense with clauses (prices, disclosure, price-beat offer) but every clause carries distinct information; only mild density cost.

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 must carry return-value expectations, and it does describe output composition for both the competitor and no-competitor paths. It does not mention length, format, or whether the comparison is generated deterministically, which leaves small gaps for a tool whose output is prose-heavy.

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 enum is self-documenting, so the baseline is 3. The description adds value by stating the parameter is optional and, crucially, explaining the semantic consequence of omitting it (generic guidance instead of a comparison), which the schema does not convey.

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 verb (head-to-head compare) and resource (vote.direct vs a named competitor), and even covers the degenerate input case (no competitor → which-platform guidance). This is distinguishable from siblings like get_platform_overview or get_price_quote 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?

It states the two call modes clearly: pass a competitor for the head-to-head, omit it for generic which-platform guidance. It does not, however, name sibling alternatives such as get_platform_overview or get_price_quote or say when this is preferable to them, so routing guidance is present but not complete.

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