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

No annotations exist, so the description carries the full burden and does a reasonable job: it discloses currency (PLN charter seat prices), the error behavior for unsupported airport codes, and the one-way case where `return_flight` is null. It omits auth/permission requirements, rate limits, and how stale the cached results may be — the `no_cache` flag hints at a cache but the description never explains its lifetime or default freshness.

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 first sentence is well front-loaded, but more than half the text enumerates the result envelope and per-itinerary fields — precisely what the existing output schema already specifies. That block is redundant bulk that pushes the actual guidance (currency, airport-list errors) into the middle. Trimming the return-shape recap would make this far easier to scan.

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 7-parameter search tool with a full output schema and no annotations, the description covers purpose, scope, currency, and the one-way edge case — enough to call it correctly. The missing pieces (cache freshness, rate limits) are minor given how much the schema and output schema already carry.

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%, so the schema already documents origin, destination, page, adults, sort_by, flight_type and no_cache. The description adds only marginal semantics beyond that — PLN pricing context and the fact that `return_flight` is null for one-way trips (which clarifies flight_type). Baseline 3 applies.

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?

Opens with a specific verb+resource+provider: 'Charter flight itineraries from Itaka.pl between a Polish origin and a charter destination.' Naming the provider and the Polish-origin scope cleanly separates it from the rainbow_* and tui_* siblings without needing their schemas.

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?

Usage is implied by the provider name and the airport-list constraint ('Only supports Itaka's fixed airport list — the error message lists valid codes'), which tells the agent what happens on a bad input. However, it never states when to prefer this over rainbow_search_charters or tui_search_charters, nor any prerequisite or exclusion beyond the airport list.

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