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

With no annotations, the description carries the transparency burden. It conveys a read-only operation via 'Retrieve' but offers no additional behavioral detail such as authentication requirements, error behavior, or response format. While safe for a read tool, it adds minimal context beyond the obvious.

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?

A single sentence efficiently lists the tool's purpose and options. Every word earns its place, with clear enumeration of the retrievable billing categories. No wasted content.

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 moderate complexity (3 params, 1 required, full schema descriptions) and no output schema, the description provides enough context: it names the four billing categories, and the schema fills in parameter details. It doesn't explain return structures, but for a simple retrieval tool this is 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?

Schema coverage is 100%, so the schema already documents all parameters and their enums. The description mentions categories like 'daily usage history' and 'spending limits' that map to action values, but it doesn't add new semantic meaning beyond what the schema already provides. Baseline 3 applies.

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 uses the specific verb 'Retrieve' and clearly identifies the resource as 'MCP billing information,' then enumerates distinct subtypes (subscription details, available plans, daily usage history, spending limits). This distinguishes it from sibling tools like get_usage by focusing on billing-specific categories.

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 for accessing billing data but provides no explicit guidance on when to choose this over get_usage or other siblings. It lacks exclusions or alternative tool references, relying on the term 'billing' to indicate context. This is implied usage rather than clear directive.

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