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

Annotations already declare readOnly/openWorld/idempotent/destructive, so they cover the safety profile. The description adds genuinely new behavioral context the annotations don't: the tool is unmetered and 'never counts against the key's allowance,' plus auth handling ('Pass api_key, or send the key as the X-API-Key header'). Quota and auth disclosure beyond annotations is solid value.

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 pricing/availability fact, then scope, then quota, then auth. Every sentence carries information, though the leading 'FREE...' line leans promotional and slightly delays the purpose statement.

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?

An output schema exists, so return values need not be described. Scope versus the sibling, quota behavior, and auth are all covered, leaving nothing an agent needs in order to call the tool correctly.

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%, including the enum for country, the api_key header note, and the subdivision region semantics, so the schema does the heavy lifting. The description adds no parameter detail beyond what the schema already states. Baseline 3 is appropriate.

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 ('public holidays') and explicitly frames scope against its sibling: 'Same as get_public_holidays, but for every country across all seven brands, not only Middle Eastern.' An agent can distinguish it from get_public_holidays 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?

The comparison to get_public_holidays ('but for every country... not only Middle Eastern') effectively tells the agent when to pick this broader tool over the narrower sibling. It stops short of an explicit exclusion clause ('use get_public_holidays if you only need Middle East'), but the routing context is clear.

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