account_usage

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering the safety profile. The description adds meaningful context by detailing the exact return fields (plan tier, billing period, credits, quota percent, API calls, subscription status) and noting the tool costs 0 credits. It does not mention any auth requirements or rate limits, but for a simple read-only usage query the transparency is solid.

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 well-structured with a concise opening summary, a clearly labeled use-case section, a credit-cost note, and two practical examples. Every line adds value, and the most important information is front-loaded.

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 and no output schema, the description is complete: it explains the purpose, return values, usage examples, and even the default month behavior. No additional context is needed to select or invoke it correctly.

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 the schema already documents the month parameter and its default behavior. The description only repeats the example (month='2026-06') without adding any new semantic meaning, such as format edge cases or timezone handling. Baseline 3 is appropriate.

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 opens with a specific verb and resource: 'Check the user's OpenEphemeris account usage and remaining credits.' It clearly states exactly what the tool does and lists the returned data. This distinguishes it from the many ephemeris and auth sibling tools, making its purpose unmistakable.

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 'USE THIS TOOL FOR' section explicitly enumerates concrete user intents and example questions, providing strong guidance on when to invoke the tool. However, it does not explicitly state when not to use it or mention alternatives (e.g., auth_status for login status), so it falls just short of a 5.

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