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

The description discloses cost (0 credits) and caching behavior (cache=true for free 24h hit), adding some transparency. However, it instructs to 'Pass cache=true' while the input schema has no parameters, creating a direct contradiction. This is misleading and undermines behavioral clarity, especially without annotations to fill the 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 short but not well-structured. It mixes output fields, cost, and caching in a single run-on sentence. While it is concise, the sequence is jumbled and the 'Pass cache=true' instruction is ambiguous. It could be reorganized for clarity.

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 description lists output fields (plan, credits, quota, renewsAt) but lacks context on return format, authentication requirements, error behavior, or how the cache feature works given the schema lacks the parameter. For a zero-param tool with no output schema, more detail is needed to fully understand the tool's behavior.

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?

With zero parameters, the baseline is 4, but the description introduces a 'cache' parameter not present in the schema. This is misleading and actively harms understanding of what arguments may be passed. Since the schema is empty and the description adds a nonexistent parameter, it fails to provide value and introduces confusion.

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 indicates the tool returns account balance information: plan type, subscription vs top-up credits, monthly quota, and renewsAt date. It effectively conveys the resource and fields, though it does not explicitly state 'get balance' or 'retrieve account balance.' It is distinguishable from siblings like usage and request history.

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?

No guidance is provided on when to use this tool versus alternatives. It mentions cost (0 credits) and caching behavior but does not state prerequisites, typical use cases, or why one would call this over related account tools. The context is minimal and lacks explicit 'use when' instructions.

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