sendcraft_get_send_time

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

With no annotations, the description must disclose behavioral traits. It states the tool returns a value and references historical open patterns, implying a read-only operation. However, it does not mention potential failure modes (e.g., insufficient data), side effects, or any special constraints, leaving the agent with incomplete behavioral context.

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 highly concise, with two sentences: the first introduces the action, and the second provides the precise output details (best day, hour, UTC, and basis). Every word is meaningful and no filler is present.

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?

While the tool has no parameters or output schema, the description conveys the semantic output but not the exact data structure (e.g., JSON keys, text format). It also omits important contextual details like behavior with insufficient historical data, making it less complete for an agent to fully rely on the return value without further clarification.

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 tool has zero parameters, so the description correctly avoids parameter details. Per the rubric, zero-parameter tools receive a baseline of 4, and the description adds no unnecessary parameter information.

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 clearly states the tool's function: it returns the best day of week and hour of day (UTC) to send campaigns for maximum open rate based on historical open patterns. This distinctly identifies the tool's purpose and differentiates it from sibling tools like send_campaign or schedule_email.

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?

The description implies when to use the tool (before sending campaigns to optimize timing) but does not explicitly state this or provide alternatives. It also lacks any mention of prerequisites, such as sufficient historical data, or cases where the tool might not be appropriate.

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