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

Annotations only cover the safety profile (readOnlyHint=true, destructiveHint=false, openWorldHint=true), so the description carries the remaining behavioral burden and does it well: it discloses result shape (rows per entity plus totals and insights[]), defines semantics of 'conversions' as the key conversion event, states money is in account currency, and warns of up to a 6-hour data lag. These freshness/currency/return-content details are exactly the value-add annotations cannot provide.

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-loads the metric list, then layers return shape, semantics, currency, and lag in short sentences before a reference URL. Mostly waste-free, though the trailing API URL is borderline padding.

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 values needn't be spelled out, yet the description still usefully sketches rows/totals/insights. Combined with full-schema param docs and annotations covering safety, an agent has enough to call it correctly; only the sibling-overlap routing is unaddressed.

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 the schema already fully documents all six parameters including the level/compact/breakdown semantics and date defaults. The description only references 'the chosen level' generically and adds no syntax or format detail beyond the schema, so the 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?

States a specific verb+resource (Reddit Ads performance) and enumerates the metrics returned (spend, impressions, clicks, CTR, CPC, conversions, CPA, ROAS), which is far better than a tautology. However, it never distinguishes itself from the closer sibling run_reddit_report, so the agent must infer the split.

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 only implied: the tool reads as the performance-reporting entry for Reddit Ads, but there is no explicit when-to-use, when-not-to-use, or alternative named despite run_reddit_report and get_ad_performance sitting alongside it. Context is sufficient to guess but not stated.

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