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

The description goes well beyond the annotations (readOnly, idempotent, non-destructive) by disclosing critical behavioral traits: it does not return live fares, returns a page URL plus IATA code, only covers 108 destinations in Europe and the Americas, and mandates that the URL must be given as an unchanged clickable link because it is the only way to book. These details are not present in the annotations and are essential for the agent to set traveller expectations and handle the response correctly.

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 appropriately sized for the tool's complexity. It front-loads the core purpose in the first sentence, then clarifies a key limitation (no live fares), explains the return behavior, and ends with actionable instructions for the agent. Every sentence earns its place and there is no redundant or filler content. The structure is logical and easy to parse.

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?

The description is complete for an agent to call this tool correctly. It covers what the tool returns (flight page or general search page, plus IATA code), the scope (108 destinations), what it does NOT return (live fares), and how the agent should present results (tell traveller to enter origin/dates, give clickable URL). The output schema exists and would detail the response structure, so the description need not repeat that. No critical information is missing.

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% – both 'lang' and 'destination' are fully described with types and examples (e.g., 'Rome, LIS, Buenos Aires'). The description adds minimal additional parameter meaning: it implies 'destination' determines which page is returned and that the page language may be controlled by 'lang', but these are already inferred from the schema. No new semantics beyond the schema are provided, so a baseline score of 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?

The description clearly states the tool's function: 'Link to search and book flights on HotelsCasa.' It specifies that it returns a flight page URL (destination-specific or general) plus the IATA code, and explicitly distinguishes itself from live-fare tools by stating it does NOT return live fares. This sets it apart from sibling search tools for other categories (hotels, activities, vehicles). The verb 'find' and resource 'flights' are 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 provides clear context on when to use this tool (to obtain a flight search page) and a key limitation ('does NOT return live fares'), which serves as a when-not. It also instructs the agent to tell the traveller to enter origin and dates on the page and to always provide the URL as a clickable link. However, it does not explicitly name alternative tools for other categories or state conditions for choosing this over siblings, though the sibling list makes that implicit.

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