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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint false. The description adds significant context: 'Every call is read-only and idempotent, so after correcting the input it is always safe to retry' and describes error handling behavior ('never raises a protocol error — it returns {"error": ...}'). No contradiction with 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?

The description is moderately long but front-loaded with purpose and premium status. Each section (purpose, example, usage guidance, error behavior) earns its place. Minor redundancy with annotations but still efficient. Could be slightly tighter.

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?

Given the tool has two parameters (no enums), an output schema, and sibling tools, the description covers all essential aspects: purpose, usage context, example, error handling, and retry safety. It is fully sufficient for an agent to correctly select and invoke this tool.

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% (all parameters documented), so baseline is 3. The description adds value beyond schema by explaining the slug comes from list_products and skill_name from the product's 'skills' array, and provides a concrete example of typical input and output. This enriches the parameter meaning.

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 clearly states the tool loads 'one paid skill's complete instructions from a product.' It distinguishes itself by explicitly mentioning it is for paid skills (not the free gateway skill) and contrasts with get_free_skill and get_full_product. The verb 'load' plus resource 'paid skill' is specific and unambiguous.

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 says 'Use when the caller wants one specific paid skill' and immediately provides exclusions: 'Not for the free gateway skill, which get_free_skill returns with no plan, and not for every skill at once (get_full_product).' This gives clear guidance on when to use and when not to, naming sibling alternatives.

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