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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds real value beyond that: it enumerates what is compared and computed, and explicitly frames output as figures only with no judgment, which shapes how the agent should present and act on results.

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 tight sentences, front-loaded with the comparison scope and dimensions, then the id source and the interpretation caveat. No filler; every clause carries information an agent needs.

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 compensates well by listing the compared fields and derived metrics. It is nearly complete for a read-only comparison tool; only edge behavior (e.g., invalid or duplicate ids) is unaddressed.

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 the single ids param already documents both its source and cardinality (minItems 2, maxItems 4). The description restates root-of-ids from search_placements but adds no syntax or format detail beyond the schema, so the 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?

Names a specific verb (compare) and resource (placements/publications) and enumerates the exact dimensions compared — price, DA, rating, turnaround, region, disclosure, indexing, categories — plus derived winners (cheapest, fastest, highest authority). This clearly differentiates it from search_placements and get_placement.

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?

"Use ids from search_placements" gives an explicit prerequisite and the source of input, and "two to four publications" constrains the use case. It stops short of naming an alternative or a when-not condition, but the workflow context is unambiguous.

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