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

Annotations cover the safety profile (readOnlyHint=true, openWorldHint=false), and the description adds what the agent cannot get from structured data: since there is no output schema, naming the returned fields (addonId, name, type, priceType, unitAmount) is genuinely useful. It doesn't mention pagination or catalog size, so not a 5.

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?

Two sentences, zero waste: purpose and return shape first, then the handoff instruction to create_booking. Front-loaded and fully earned.

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 zero-param read-only list tool with no output schema, the description supplies both the catalog scope and the return fields, which is everything an agent needs to select and chain 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?

Zero parameters, so the baseline is 4. The description correctly points out that addonId is the value to reuse downstream, which is the only 'parameter-like' semantic an agent needs.

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 ('Fetch the catalog of bookable add-on extras') with concrete examples (wine, flowers, activities). An agent can tell it apart from get_fact_sheet, get_hotel_details, and search_availability without opening any 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?

Explicitly routes the agent forward: 'Use addonId values when adding addons to create_booking,' naming the sibling that consumes this output. No when-not or exclusions are given, but the primary usage context is unambiguous.

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