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

Annotations already cover the safety profile (readOnlyHint=true, destructiveHint=false, openWorldHint=true), so the bar is lower, and the description clears it by disclosing non-obvious behavior: the data_coverage flag exists so a null demand reads as a coverage gap rather than zero sales, demand carries a source/badge_band/confidence, and ratings carry a rating_coverage flag. It stops short of auth requirements or rate limits.

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 purpose and the usage triggers are front-loaded, and with no output schema in place the return-field enumeration genuinely earns its space. The middle is a single run-on sentence that is dense and hard to scan, which costs a point.

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?

There is no output schema, so the description must carry the return contract, and it does: score range, the five named dimensions, demand fields with confidence metadata, coverage flags, rating/review data, brand dominance, red flags, and fulfillment split. An agent knows exactly what it gets back and how to interpret the null cases.

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 all three parameters including the marketplace_id enum mapping and the qty ROI-sizing note are already documented in the schema. The description adds nothing parameter-specific (qty is never mentioned in prose), 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?

States a specific verb+resource with explicit scope ('a single ASIN for FBA sourcing'), immediately distinguishing it from evaluate_brand, evaluate_category_for_private_label, and the broader find_sourcing_opportunities siblings.

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 concrete trigger phrases ('should I buy this?', 'how fast does this sell?', shares an ASIN and wants a sourcing recommendation), which is clear contextual guidance. However it names no alternatives or exclusions — e.g., it never says to prefer asin_profit_calc for pure ROI math or product_dossier for a full profile, even though those siblings overlap.

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