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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds substantial data-semantics context beyond them: cumulative running totals rather than per-day deltas, one row per account per sync day, the 180-day range cap, and the exact metric fields returned. This is the behavior an agent most needs to avoid misinterpreting the numbers.

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 definition, then the row shape and metric list, then the caveats. Most sentences earn their place, though the cumulative-vs-daily warning is stated twice ('NOT activity that happened on that day' and 'not daily views or follower growth'), which is mild redundancy.

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, the description usefully enumerates the returned columns (date, platform, cumulative totals, averageEngagementPct), which is exactly what is needed without a formal return spec. Gaps remain on `brandId`, row volume/pagination limits, and explicit alternative-tool routing, but these are minor against the otherwise rich data semantics.

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 0%, so the description carries the burden and mostly succeeds: it explains `from`/`to` format, inclusivity, and the 180-day cap, and labels `platform` as an optional filter. It does not explain `brandId` at all, leaving 1 of 4 parameters undocumented in both schema and description.

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 (per-sync daily metric snapshots of the brand's video posts) and precisely scopes what the data is: cumulative running totals, one row per account per sync day. It even distinguishes itself semantically from adjacent concepts (not daily activity, not follower growth), letting an agent tell it apart from siblings like get_audience_growth or get_performance_summary.

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?

Clear about context: it defines the accepted date format and a hard cap (last 180 days before `to`), and explicitly rules out misreads ('NOT activity that happened on that day', 'not daily views or follower growth'). However, it never names an alternative tool to use for daily-view or follower-growth questions, so routing against actual siblings is left implicit.

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