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

Beyond the annotations (readOnlyHint=false, idempotentHint=true), the description discloses the asynchronous job pattern (first call returns started, a repeat with identical args returns done/running 'usually within a minute'), idempotency semantics, and persistence ('kept and published at a page address'). It also constrains content ('nothing is invented, and prices and stock are not in it'), which the annotations cannot convey. No contradiction with 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, async behavior, and alternatives are front-loaded before the error taxonomy, and the dense error-recovery block earns most of its length given there is no output schema or structured error field. It loses a point for minor redundancy such as the inline 'Example call' that duplicates the schema's own example and the pointer to the full guide.

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 fully specifies the return value (short answer, one-row-per-product table, cited facts with source links, published page address), the polling pattern, and a per-error-code recovery path. Nothing an agent needs in order to call and re-call this tool correctly is missing.

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%, so the schema already documents merchant, product_id, question, and the products array bounds. The description restates the 2–8 product range and the question-only mode rather than adding syntax or format detail beyond the schema. Baseline 3 is appropriate when the schema does the heavy lifting.

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 first sentence states a specific verb and resource with its output shape: 'Writes a comparison of products ... a short answer, a table with one row per product and a cited fact in every cell.' It also distinguishes itself from siblings by naming search_catalog and check_product as alternatives. An agent can identify the tool's job without opening the 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 when to reach for it ('a side-by-side of checked facts on products the person is choosing between, including ones found with search_catalog') and when to route elsewhere, e.g. 'COMPARE_UNAVAILABLE means comparisons are not running, so compare with check_product.' Prerequisites are explicit: a named product needs checked facts, so enrich_product first for one that has none.

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