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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds the 2-5 account bound and metric scope, but says nothing about return shape, whether missing/private accounts cause errors, or data freshness — modest added value beyond the annotations.

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 sentences: capability first, usage triggers second. No filler, no repetition of schema details beyond what a reader needs.

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 a note about what the comparison returns (per-metric ranking? side-by-side table?) would help. Otherwise the definition covers inputs, scope, and intent adequately for a read-only analytics tool.

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% with enums and defaults documented for both metric and period, so the schema carries the load. The description's metric list roughly mirrors the enum (though 'posting frequency' does not match the actual enum value 'posts_count'), adding little beyond it.

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?

Specific verb ('Compare') plus resource ('2-5 Instagram accounts side by side') and an enumerated metric set. The Instagram scoping and multi-account comparison framing separate it cleanly from get_account_stats and compare_tiktok_accounts.

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?

Explicit when-to-use triggers: benchmarking, competitor comparison, ranking best performer. It stops short of naming alternatives or exclusion conditions (e.g., use get_account_stats for a single account), so it is strong but not fully routing.

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