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

With no annotations, the description carries the burden and mostly succeeds: it discloses the data source, the currency (PLN), that prices are per-person charter seat prices, and what fields each result carries. It doesn't discuss rate limits, freshness/caching guarantees (the no_cache param exists but its implications aren't elaborated), or whether results are paginated.

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?

Front-loaded with the core purpose and the disambiguation sentence early. The trailing result-shape block is somewhat long and partly redundant given an output schema exists, but it is purposeful because the key naming is genuinely confusing ('flights' holds destinations).

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?

An output schema exists, so return-value detail is technically redundant, but the description highlights the one trap (the `flights` key contains destination records, not flights) that an agent would otherwise get wrong. Coverage of filtering semantics and the no-annotation safety profile is adequate for a read-only search 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 description coverage is 100%, so every one of the seven parameters is already documented in the schema. The description only loosely restates 'optional destination/origin/date filters' and adds the per-person price semantics; it adds little syntax or meaning beyond what the schema provides.

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 ('charter flight destinations sold by Rainbow Tours') plus the source site, and explicitly distinguishes itself from the sibling rainbow_search_outbound. An agent can tell instantly that this is a destination-level charter search, not a day-by-day flight search.

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?

Names the alternative rainbow_search_outbound and the condition that selects it ('day-by-day flights to one destination'). It does not address the two competitor-source siblings (itaka_search_charters, tui_search_charters) or when to prefer Rainbow over them, so routing across providers is left to inference.

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