Get OU cost breakdown

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

Annotations already declare readOnlyHint=true and destructiveHint=false, so description need not repeat. Description adds requirement info (Pro plan) and parameter behavior. No contradiction.

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?

Extremely concise: one sentence for purpose, one for context/requirement, one for parameter, and three example queries. No wasted words, front-loaded with core action.

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 tool with one optional parameter, no output schema, and clear annotations, the description covers purpose, prerequisite, parameter semantics, and example use cases. Complete and sufficient.

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?

Single parameter 'days_back' is explained with 'Look-back period in days (default 30)' despite 0% schema description coverage. Provides default value and usage context, compensating for lack of schema documentation.

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?

Description clearly states 'Break costs down by AWS Organizational Unit (OU)' with a specific verb and resource. It differentiates from siblings by mentioning mapping to departments/teams for chargeback, distinguishing it from get_costs_by_team and get_label_costs.

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 states prerequisite: 'Requires a Pro plan (org_reports).' Provides example queries and context for when to use (when OUs map to departments). Does not explicitly exclude alternative tools, but the sibling list and description imply differentiation.

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