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

With no annotations, the description carries the full burden and does well: it discloses the return contents, the minimum-sample threshold, the verdictAvailable flag, and an explicit instruction not to present numbers as a judgement below that threshold. It omits any statement about read-only safety, unknown-ID behavior, or caching, which keeps it short of 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?

Four dense sentences, front-loaded with the core question and its distinguishing scope, followed by return contents, the caveat, and the ID source. No filler and no repetition of schema fields.

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 and no annotations, the description still covers what the agent needs: the judgement semantics, the returned fields including buyUrl, the low-data guardrail, and where IDs come from. Nothing essential for correct invocation 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 coverage is 100%, so both id and the days enum (30/60/90, default 90) are already documented in the schema. The description only alludes to the window via 'window low, high and mean' and the ten-price threshold; it adds no format or selection guidance beyond the schema, so 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?

States a specific verb and resource — judge whether a tracked product is cheap right now — and immediately scopes it as 'by its own recorded history rather than against other products', which separates it from get_best_value and get_price_index. It also enumerates what the answer contains (window low/high/mean, distance above low, verdict, buyUrl).

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?

Gives a concrete applicability rule (fewer than ten recorded prices means verdictAvailable is false and no verdict should be presented) and routes the agent to search_products for the required ID. It does not explicitly say when to prefer get_price_history over this tool, so the sibling boundary on the history side is left implicit.

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