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

Annotations already establish read-only, idempotent, open-world, non-destructive behavior. The description adds useful context beyond that: results are engagement-weighted, based on the account's own history, expressed in UTC, and include concrete upcoming datetimes. It does not discuss authentication or rate limits, but for a simple read tool this is a solid level of disclosure.

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?

The description is one tight sentence that front-loads the core output and follows with the actionable use case. Every clause earns its place, with no repetition or filler.

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 simple read-only tool with no output schema, the description successfully communicates the return shape (day, hour, UTC, upcoming datetimes) and the recommended usage context. Annotations and the fully described parameter cover the rest, leaving no critical gaps.

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?

The schema has 100% description coverage for the single platform parameter, so the schema already carries the parameter documentation. The description does not add any platform-specific semantics or filtering guidance, so it sits at the baseline of 3.

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?

The description names a specific output (engagement-weighted best times to post by day and hour in UTC) and a specific data source (the account's own history). It also distinguishes itself from generic scheduling tools by stating it returns concrete upcoming datetimes. This is more than enough for an agent to identify the tool and its unique purpose.

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?

It gives clear positive guidance: 'Use before scheduling to maximise reach.' This tells the agent exactly when the tool is relevant. It does not mention when not to use it or name alternative tools, so it falls just short of a 5.

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