get_usage_summary

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. It implies a read-only operation ('Get'), but doesn't specify if it requires authentication, has rate limits, returns real-time or cached data, or what happens if the subscription_id is invalid. For a tool that retrieves billing information, this is a significant gap in transparency.

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 a single, efficient sentence that directly states the tool's purpose without any unnecessary words. It's front-loaded with the core action and resource, making it easy to parse quickly. Every part of the sentence earns its place by conveying essential information.

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's complexity (simple parameter, no output schema, no annotations), the description is minimally adequate. It covers what the tool does but lacks details on behavior, usage context, and output format. Without annotations or an output schema, the agent must infer these aspects, making the description incomplete for optimal tool invocation.

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 input schema has 100% description coverage, with the parameter 'subscription_id' clearly documented as 'Stripe subscription ID (stored after setup_metered_billing)'. The description doesn't add any extra meaning beyond this, such as format examples or validation rules. Given the high schema coverage, a baseline score of 3 is appropriate as the schema handles the heavy lifting.

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 current billing period usage and estimated cost for metered billing.' It specifies the verb ('Get') and resource ('usage and estimated cost'), making it easy to understand what the tool does. However, it doesn't explicitly differentiate from sibling tools like 'estimate_cost' or 'check_balance', which might have overlapping or related functionality.

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 no guidance on when to use this tool versus alternatives. It doesn't mention any prerequisites, such as requiring a metered billing setup, or compare it to siblings like 'estimate_cost' or 'check_balance'. This lack of context could lead to confusion about tool selection in a scenario with multiple billing-related options.

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