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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered; the description adds genuinely non-structured context with the $0.05 per-call cost, USDC-on-Base x402 payment requirement, and what the live snapshot contains (weekly share, discount from retail). It stops short of covering failure modes (e.g., payment failure, empty results) or result pagination, which keeps it from 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?

Two dense sentences with the deliverable front-loaded and the cost/payment constraint last; the parenthetical output enumeration is information-bearing rather than filler. Nothing is repeated from the title or schema.

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 eight parameters, the description carries the return-value burden well by enumerating the summary metrics and listing fields, and it discloses the payment model. Minor gaps remain around pagination and behavior on zero results or payment errors.

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% and every parameter carries its own description and enums, so the description adds little parameter-level meaning beyond restating the keyword and the 100-listing cap. Baseline 3 applies 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?

States a specific verb and resource (live Poshmark listings for a keyword) plus the platform identity (US fashion resale), which cleanly separates it from vinted_search, reverb_search, and ebay_market siblings without needing their schemas. It also names the two-part return (market summary plus listings), so the agent knows what it gets.

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 implied by the platform scope — call this when you need Poshmark-specific data — but there is no explicit when-to-use/when-not or pointer to an alternative such as compare_resale for cross-platform work. The agent must infer that routing from the sibling names alone.

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