billing_get_cost_breakdown_by_service

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. The description mentions it returns 'Service-wise cost breakdown with percentages' but doesn't disclose whether this is a read-only operation, whether it aggregates data, what time period defaults apply, or any other behavioral traits. For a billing tool with no annotations, this is a significant gap.

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 concise and front-loaded with the main purpose. The Args and Returns sections are clearly structured and add useful information without excessive verbosity. It's appropriately sized for a simple one-parameter tool.

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?

The tool has an output schema and only one optional parameter, so the description doesn't need to explain return values in detail. However, given the large number of billing sibling tools, the description could benefit from clarifying how this differs from billing_get_monthly_usage_summary or billing_analyze_spending_trends. The lack of behavioral context (e.g., whether this is read-only) is a gap.

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 description coverage is 0%, so the description must compensate. The description does explain the 'days' parameter ('Number of days to analyze (default: 30)'), which matches the schema's default of 30. However, it doesn't add much beyond what the schema already shows, and there's no additional context about valid ranges or behavior for different values.

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: 'Get cost breakdown by service for the specified period.' This is a specific verb+resource combination that distinguishes it from other billing tools like billing_get_current_balance or billing_list_billing_history. However, it doesn't explicitly differentiate from sibling billing tools like billing_get_monthly_usage_summary, which could also provide cost breakdowns.

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 usage context by mentioning 'for the specified period' and the days parameter, but it doesn't explicitly state when to use this tool versus alternatives like billing_get_monthly_usage_summary or billing_analyze_spending_trends. There's no when/when-not guidance or mention of alternatives.

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