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

The readOnlyHint annotation is reinforced and expanded by the description's note that plan, seat, and top-up changes require human action in the web app. This adds behavioral context beyond the annotation, such as the requirement for organizational context and the absence of write capabilities.

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 concise, using three sentences to convey the tool's purpose, optional parameter behavior, and constraints. It is well-structured with no redundant 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?

For a read-only tool with no output schema, the description fully covers what the tool returns, how to invoke optional features, and important contextual requirements. Nothing essential is missing.

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 schema already documents all three parameters with 100% coverage; however, the description adds semantic value by explaining that includeHistory reveals 'where the credits went — per day and per feature', clarifying the purpose of the parameters in context. This goes slightly beyond the schema descriptions.

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 identifies the tool as retrieving the AI credit balance, enumerating its components (remaining, plan, rollover, top-ups, reset), and distinguishing it from siblings by its specific resource. The verb 'Get' and resource 'AI credit balance' are explicit.

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 practical guidance: it explains how to enable optional history via includeHistory, notes that organization context is required, and clarifies that mutations are not available. While it does not explicitly name alternative tools, no sibling tool serves this purpose, so guidance is adequate.

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