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

The readOnlyHint annotation already tells the agent this is a safe read, and the description adds the temporal scoping ('current period'). It says nothing about permissions, whether data is real-time or cached, or the shape of the response, so it adds only modest value beyond annotations.

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?

Two tight sentences with the purpose front-loaded and the endpoint reference appended usefully. No filler, though the endpoint restates callable information the agent already has via the name.

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 read-only tool with fully documented parameters and no output schema, the definition covers what is needed to call it correctly. The only omission is explicit differentiation from the sibling past-usage tool.

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 100%, so all three parameters carry their own documentation, establishing the baseline of 3. The description adds no extra meaning about the required subscription ID or the apply_taxes flag beyond what the schema already states.

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?

States a specific verb (retrieve), resource (usage-based billing data), and scope (current period), plus the underlying API endpoint. It implicitly distinguishes itself from lago_get_customer_past_usage via 'current period', but never names that sibling, so a 4 rather than a 5.

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 phrase 'for the current period' implies the usage context versus past usage, but there is no explicit when-to-use/when-not guidance or named alternative. Adequate but leaves the agent to infer the routing against lago_get_customer_past_usage.

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