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

Annotations already cover the read-only/idempotent/destructive profile, so the bar is lower, and the description still adds non-obvious aggregation semantics: snapshots are never summed repeatedly and missing metrics are not treated as zero. This is genuinely useful behavioral context beyond the structured fields, though it does not touch auth, scoping, or latency.

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?

Four short sentences, front-loaded with the core purpose and zero filler. Each remaining sentence adds a distinct, load-bearing fact (aggregation caveat, exclusion, routing alternatives).

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 an output schema present, return values need not be explained, and annotations carry the safety profile; the description completes the routing and aggregation picture. The only real shortfall is the absence of any parameter-level guidance for a 3-param, 0%-coverage schema.

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 must carry parameter meaning, but it names none of brandId/since/until. It only implicitly clarifies the period semantics ('posts published in the selected period'), which usefully distinguishes publish-window from activity-window filtering, leaving brandId entirely unexplained.

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 and resource ('Summarize the latest saved lifetime metrics for posts published in the selected period') and explicitly rules out the adjacent concept ('Not daily account activity'). An agent can distinguish this from get_analytics and the report tools without opening a schema.

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?

Names the alternatives and the condition that selects each: saved X/channel reports via get_report_capabilities + get_channel_report, fresh reports via request_channel_report. It also excludes the daily-activity case, giving both when-to-use and when-not-to-use.

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