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

Beyond readOnlyHint/openWorldHint, the description discloses the critical operational constraints: only the first page of the feed is read, ordering is newest-first, and each successful call costs $0.002 USDC via x402 on Base/Solana/Arc while failed calls are free. The pricing and payment-rail detail is exactly the kind of behavior an agent cannot get from 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?

Three tight sentences: what it returns, the page/ordering constraint, then cost and payment terms. Front-loaded with the payload and no filler.

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?

For a single-optional-parameter read tool with an output schema, annotations, and an explicit cost model, nothing needed to call it correctly is missing. The output schema already documents return values, so the description does not need to.

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?

With 100% schema coverage on the single 'limit' parameter, baseline would be 3, but the description adds meaning the schema lacks: results come from the feed's first page in newest-first order, which tells the agent what the limit is actually slicing. It still doesn't restate the 1-30 range, but the schema already covers that.

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 names a specific source (Mood Fabrics' public product feed) and enumerates exactly what is returned: title, type, variant prices, and per-variant stock. Against 50+ sibling ecommerce_* store tools, naming the store and the record shape is enough for an agent to pick this one 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?

Usage is only implied: an agent infers it should call this when it needs Mood Fabrics fabric catalog data. There is no explicit when-to-use/when-not statement and no routing to an alternative sibling (e.g., a broader fabric or multi-store search tool), though the narrow single-store scope makes the implied case fairly obvious.

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