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

Annotations already declare readOnly/idempotent/no-destructive, so the safety profile is covered. The description adds genuine behavioral context beyond that: each channel's metric field distinguishes real engagement data from publish-volume-only channels, with an explicit warning not to present a posts-only channel's zero engagement as a real result.

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 what/scope in the first sentence, then a focused caveat about interpreting the metric field. Two sentences, no padding, each carrying load.

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, so the description must characterize return values, and it does: daily per-channel metrics plus change vs. the previous period. Combined with the metric-field caveat, an agent has enough to call and interpret it, though it lacks any note on absent/history limitations.

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% and the single 'days' parameter already documents its enum and default in the schema. The description mentions the same 7/30/90 windows but adds no format or semantics beyond the structured field, so 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 (Get) and resource (per-channel daily trends) and enumerates what is returned: posts published/failed, engagement, impressions, totals, and period-over-period change. It is clear on its own, but it never names or contrasts with overlapping siblings like get_stats, get_growth_overview, or get_trend_performance, so an agent must infer the boundary.

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 7/30/90-day framing implies it is for windowed trend analysis, but there is no explicit when-to-use, when-not, or alternative-selection guidance. With several adjacent analytics tools (get_stats, get_growth_overview, get_trend_performance), leaving routing to inference is a real gap.

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