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

Annotations already declare readOnlyHint, openWorldHint, and destructiveHint=false. The description adds useful context beyond them: it says dates with no slots are omitted, describes the return content (open dates/time slots and price per unit type), and specifies the auth requirement ('Needs the user's Cotlet API key with access to this app').

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 front-loaded with purpose and ends with auth requirements, which is structurally sound. However, the first two sentences are largely redundant — both state open dates/time slots and price per unit — so not every sentence fully earns its place.

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, the description does explain return values (open dates, time slots, price per unit type, omission of dates with no slots), and annotations cover the safety profile. It could clarify that omitting package_id returns all packages, but overall it is complete enough for an agent to call 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 coverage is 100%, and the schema descriptions already explain each parameter's source (activity_id from search_activities, package_id from get_activity, from/to date range). The description mentions package and date range generically but adds no syntax, format, default, or scoping details beyond the schema, so baseline 3 applies.

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: 'Open dates and time slots for a package, with the price per unit (adult, child).' It distinguishes from siblings by naming book_activity and amend_booking, making clear this is a pre-booking availability check rather than a booking or amendment operation.

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?

Explicitly says 'Run it before book_activity or amend_booking so you only ask for a slot that exists,' giving a clear when-to-use condition. It lacks explicit when-not guidance or alternative availability tools, so it is a 4 rather than a 5.

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