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

Annotations already declare readOnly, idempotent, non-destructive, non-open-world behavior, so safety needs no restating. The description adds real value beyond them: the result is aggregate dates/days with no per-flight rows, and roundtrip requests also return a return leg. It stops short of noting data freshness/caching or how the range is bounded, which would be the remaining behavioral gap.

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, then the boundary against search_flights, then format conventions. Every sentence carries signal, though the final sentence about the calendar rendering below the search_flights card is UI-implementation detail that is somewhat tangential to invocation.

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?

With an output schema present, the description need not explain return values, and it still clarifies that results are fares-per-date rather than flight lists. Combined with full schema coverage and clear read-only annotations, an agent has everything needed to call this correctly.

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 baseline is 3 and the schema already documents every field including defaults and the trip_type semantics. The description reinforces the IATA and ISO conventions, which is mildly useful but largely repeats what the schema states, so it does not exceed the baseline.

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 ('Shows a Paytm fare calendar: the cheapest flight fare for every date in a range') and draws the boundary against the sibling search_flights by stating it lists no individual flights. An agent can tell instantly which of the two flight tools to pick.

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?

Explicit when-not guidance: 'requests to show or find flights are served by search_flights.' It also gives a concrete co-selection condition (short window, sort_by='cheapest' on a date in that window, same route), which tells the agent how this tool pairs with search_flights rather than replacing it.

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