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 context: the previous period is auto-derived as an equal-length window immediately before, and new nationalities return previous_period: null with change expressed as 100% growth — useful edge-case behavior the annotations do not convey.

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?

Markdown headers front-load Overview, When to Use, What You Get, and Quick Start, and the content is scannable. It is longer than strictly necessary for a three-parameter read tool, with some overlap between 'What You Get' and the overview paragraph, but nothing is wasted.

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 thoroughly covers the return shape: period metadata, summary totals, per-nationality booking/sales/average metrics, and the new-market null case. Combined with the annotations covering safety, an agent has everything needed to call and interpret this 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%, so the baseline is 3, but the description adds meaning beyond the schema: it names from/to/sandbox as the query inputs and explains that the API derives the prior comparison period from them rather than requiring a separate parameter.

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?

The description states a specific verb and resource: analytics on guest-nationality source markets of bookings, with period-over-period comparison. It is clear what the tool produces, but it does not differentiate itself from the very similar sibling get_bookings_source_markets_report, so an agent must guess which report 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?

Four explicit 'When to Use' bullets give concrete scenarios (source market analysis, period comparison, geographic dashboards, marketing planning), which is well above implied usage. It stops short of an exclusion or an alternative-tool pointer, which would be needed for a 5.

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