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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior, but the description adds meaningful behavioral context beyond them: full bodies are paid, while free outlines, provenance, formats, and exact prices are returned. It clarifies the paywall boundary and the data shape without contradicting any annotation.

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 carry the full message: what the tool does, what it returns, and which sibling to call next. The most important purpose information is front-loaded, and no sentence is wasted.

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 no-parameter read-only listing tool with an output schema, the description is complete: it states return contents, the paid/free split, and follow-up actions. The annotations cover safety and idempotency, so nothing essential 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?

This tool has zero parameters, so the schema trivially covers 100% and there is no parameter burden for the description to carry. Per the baseline for 0-param tools, a 4 is appropriate; the description correctly avoids inventing parameter details.

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?

Description opens with a specific action and resource: 'Compare premium skills and multi-fix bundles.' It then lists concrete outputs (ids, free outlines, provenance, formats, exact prices), making the tool's function unmistakable. It also names related sibling tools get_skill and search_fixes, so an agent can tell them apart.

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?

The description explicitly routes the agent to the correct next tool: 'Call get_skill with a chosen id for signed USDC and ETH checkout; use search_fixes for a single error.' This gives clear when-to-use direction and names alternatives, satisfying the highest bar for usage guidance.

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