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

With no annotations, the description carries the full burden. It discloses that results are 'actually fetched now', that it returns price=None with confidence='none' when no machine-readable price exists, and that extraction source is provided as evidence. It also exposes metering cost, which is a useful disclosure.

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?

The description is appropriately concise for the information conveyed, using a few punchy sentences. The pricing note at the end is extra but relevant. Front-loaded with 'Ground-truth retail oracle'.

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?

The description explains the return values (price, currency, in-stock, source, confidence), failure behavior, and use case. Without an output schema, this is adequate. It doesn't cover error cases but they are minor.

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%, so baseline is 3. The description does not add specific parameter semantics beyond what the schema already provides (e.g., expect_price is described only in 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 clearly identifies the tool as a ground-truth price oracle for retail product URLs, specifying it fetches current price, currency, in-stock state, and extraction source. It distinguishes from siblings like market_rank or merchant_fact_check by emphasizing real-time fetch and evidence-based extraction.

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 explicitly states when to use: 'Use before an agent quotes, compares, or transacts on a price it would otherwise invent.' It also clarifies it covers no-API shops and never guesses, implying limits. However, it doesn't name alternative tools or explicitly say when not to use, so slightly below a 5.

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