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

Annotations already declare read-only, idempotent, non-destructive, open-world behavior, so the bar is lower. The description still adds real value: it is an estimate-only tool with no live fare lookups, and results are cached for a minute per parameter set — both material to an agent deciding how often to call it. It also clarifies that 'friday' is echoed rather than priced, preventing a misuse of that parameter.

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?

Purpose is front-loaded and the second sentence carries the two critical constraints (estimates only, caching). The first sentence is a dense semicolon-separated clause chain that takes effort to parse, but no sentence is filler.

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?

There is no output schema, and the description compensates well by enumerating the return shape: totals, per-person and flight figures per (city, persona), cheapest persona per city, plus party_shapes. Caching and the estimate-only nature cover the main behavioral unknowns. It doesn't hint at result size or cardinality, which is the one remaining gap for a sweep-everything tool.

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% with enums on tier and month, so the schema already carries all parameter meaning. The description restates the knob set (tier, month or year average, group, optional origin) without adding syntax or defaults beyond what the schema documents. Baseline 3 is correct.

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: prices every published itinerary at once, broken down per (city, persona), for a tier/month/group/origin. The scope is unmistakable and clearly batch-oriented. It stops short of naming estimate_itinerary as the single-itinerary counterpart, so differentiation from that sibling is left implicit.

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?

'Estimates only, no fare lookups' explicitly excludes the get_fare path, and 'Every published itinerary priced at once' signals the bulk-sweep use case. No explicit instruction about when to prefer estimate_itinerary or how large a result set to expect, so the guidance is clear but not exhaustive.

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