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

With no annotations, the description carries the full burden of behavioral disclosure, and it excels: it explains the tier selection ('fewest-stops tier... never a mix'), sorting ('sort by flying time'), layover cap ('c ap at 7'), and charter handling ('excluded unless include_charter=true, and never appear inside multi-leg itineraries'). This is rich, non-obvious behavior that an agent needs to know.

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 dense but purposeful: four sentences, front-loaded with the core function, then behavioral rules, then data scope. Every sentence adds distinct value with no filler or redundant restatements.

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 conveys strong behavioral context but lacks an output schema and never states the shape of returned options (e.g., what fields each connection contains). It also omits the max_flying_min parameter. For a tool with zero annotations and no output schema, this leaves meaningful gaps in the agent's ability to fully use results.

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 0%, so the description must explain parameters. It covers from_airport/to_airport as airport codes, max_stops in the tier logic, and include_charter explicitly. However, it never mentions max_flying_min, leaving that parameter's meaning entirely to the agent's inference.

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 opens with a specific verb and resource: 'Find flight connections between two airports (airport codes).' It clearly distinguishes this tool from siblings like airport_destinations (which lists destinations), resolve_airport (which resolves codes), and route_detail (which gives route details) by focusing on pair-wise connection search with explicit tier logic.

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 about when to use the tool: it returns scheduled passenger routes, explicitly stating 'not fares, not booking, not date-specific schedules,' which helps an agent avoid using it for pricing or booking. However, it does not explicitly name alternatives or state when to prefer this over airport_destinations or route_detail.

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