get_usage_historical_costs

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It adds important context about data availability timing and access restrictions for parent-level organizations. However, it doesn't describe the return format, whether this is a read-only operation, potential rate limits, or error conditions. For a tool with zero annotation coverage, this leaves significant behavioral gaps.

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 perfectly concise and front-loaded. The first sentence states the core purpose, followed by two critical constraints. Every sentence earns its place with essential information. There's zero wasted text or redundancy.

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?

Given the tool has no parameters (simple complexity) but also no annotations and no output schema, the description should do more to be complete. While it covers purpose, timing constraints, and access restrictions, it doesn't describe what the tool returns (cost data format, time periods covered, etc.). For a usage/cost reporting tool with no structured output documentation, this leaves the agent guessing about the response structure.

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 0 parameters with 100% schema description coverage, so the schema fully documents the lack of parameters. The description appropriately doesn't discuss parameters, which is correct for a parameterless tool. A baseline of 4 is appropriate since the description doesn't need to compensate for any parameter documentation gaps.

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 purpose: 'Get historical cost across multi-org and single root-org accounts.' It specifies the verb ('Get'), resource ('historical cost'), and scope ('multi-org and single root-org accounts'). However, it doesn't explicitly distinguish this tool from sibling usage tools like 'get_usage_billable_summaries' or 'get_usage_estimated_costs', which prevents a perfect score.

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 provides clear context about when to use this tool: 'Cost data for a given month becomes available no later than the 16th of the following month' and 'This endpoint is only accessible for parent-level organizations.' These are helpful usage constraints. However, it doesn't explicitly state when NOT to use this tool or name alternative tools for different usage scenarios, which would be needed for a score of 5.

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