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

Annotations already declare readOnly/idempotent/non-destructive, but the description adds genuinely new context: a premium license requirement, an explicit error contract (never raises a protocol error, returns {"error": ...} with a fix hint), and retry safety after correction. A concrete input/output example further sets expectations for success responses.

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?

Front-loaded with the core action, then constraints and error behavior in a logical order. Slightly bloated by an inline JSON example and the awkward 'PREMIUM (license).' fragment, but no sentence is redundant.

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 an output schema present, the description needn't document return values, yet it still covers selection semantics, sibling routing, license gating, and error/retry behavior. An agent has everything needed to call it correctly and handle failures.

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%, so baseline is 3; the description adds marginal value with a worked example ({"slug": "thesis-advisor", "skill_name": "Outline Builder"}) and a statement that selection is by skill_name. It does not add format rules beyond the schema's 'exactly as returned by list_products'.

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: 'Load one paid skill's complete instructions from a product,' including the returned shape. It explicitly distinguishes itself from get_free_skill and get_full_product, so an agent can route correctly without opening either 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?

Gives an explicit when: 'Use when the caller wants one specific paid skill.' Then names both alternatives and their exclusion conditions — the free gateway skill (get_free_skill) and all skills at once (get_full_product). Nothing is left to inference.

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