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

Annotations already cover read-only and closed-world safety, so the bar is lower; the description still adds that results derive from historical engagement and arrive as a heatmap, which is the key behavioral detail given there is no output schema. It omits the lookback window and what happens when an account has too little data.

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?

Three tight sentences: what it does, what it returns, when to call it. No filler and the core action is front-loaded.

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?

For a one-parameter read tool with no output schema, the description supplies the return format and the data source, which is most of what an agent needs. Minor gaps remain around data window and empty/insufficient-data behavior.

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 'username' parameter is fully documented in the schema including the 'without @' convention. The description adds no parameter-level meaning beyond that, 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 and resource ('Find the best days and times to post on Instagram') plus the data basis ('historical engagement data') and the return shape ('heatmap'). The platform qualifier cleanly separates it from get_tiktok_best_posting_times without needing the 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?

Explicitly enumerates trigger phrasings: 'when someone asks when to post, what the best posting schedule is, or how to optimize their posting times.' No explicit when-not or named alternative, though the Instagram framing implicitly excludes the TikTok sibling.

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