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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety is fully covered by structured data. The description adds the useful nuance that results come from 'saved data' (not a live query) and spells out the returned funnel metrics, but it does not address freshness, latency, or data windows beyond that.

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?

Two tight sentences, front-loaded with the core purpose, followed by a compact enumeration of the return contents. No filler and nothing redundant with the schema.

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 no output schema available, the description carries the burden of explaining the return shape, and it does so well by listing the steps, benchmark comparison, trend, and worst-losing step. It stops short of 5 only because it says nothing about the metric's timeframe or how to interpret the benchmark.

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?

There is only one parameter and schema_coverage is 100%: the schema already explains the brand_id fallback behavior ('most recently updated brand'). The description adds nothing about this parameter, so the baseline of 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?

The description states a specific verb and resource ('Get the sales funnel from ad click to purchase') and even enumerates what each step contains, so the tool's job is unambiguous. It does not explicitly distinguish itself from siblings like get_performance or get_ad_fatigue, so it stops short of a 5.

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?

The framing 'from ad click to purchase' implies the conversion-analysis context in which this is relevant, and 'Read only, saved data' implies it is a cheap lookup, but there is no explicit when-to-use statement, no prerequisites, and no named alternative such as get_performance. Usage is inferable rather than stated.

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