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

Annotations declare readOnly, idempotent, non-destructive. The description adds valuable behavioral nuance beyond that: cached data with cached_at/age_minutes, package totals not per person, party_match=false semantics, and the strict rule that a price belongs only to its own date. These are critical to correct use and not present in annotations.

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?

Dense but every sentence earns its place. The main function is front-loaded, followed by usage routing, then three essential caveats about cache, pricing units, and date-attachment. Despite length, no filler or repetition.

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 read-only, single-parameter, no-output-schema tool, the description covers purpose, when to use it, data provenance, unit semantics, and the most dangerous misuse (misattributing a price to a different date). Nothing critical 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?

Input schema covers the single 'destination' parameter 100%, including the note that omitting it returns every destination. The description does not add meaning beyond the schema; the main value is in interpreting returned rows, not in parameter syntax.

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?

Description opens with a specific verb and resource: 'Cheapest flight+hotel charter packages from Tirana (Albania) per destination, from the live booking-engine cache.' It further clarifies it returns the 5 cheapest per destination, each on its own date. This clearly distinguishes it from siblings like charter_offers.

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 states when to use: 'Use for "what is the cheapest…" only; for advice or filtering use charter_offers.' It also warns that prices are cached and not live queries, setting correct expectations about freshness.

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