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

Annotations already establish that the tool is read-only, idempotent, and non-destructive. The description adds useful specificity about the scoped resource ('flowmusic credits') and what is reported (remaining balance and subscription tier), which goes beyond the annotations without contradicting them.

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 clear sentence with no filler. The core action and object are front-loaded, and every word contributes useful 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 parameterless read-only check, the description supplies the essential context: what resource is being queried and the two pieces of information returned. It doesn't describe exact output formatting or field names, but the low complexity and strong annotations make that a minor gap.

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 tool has zero parameters and the schema covers everything about parameters; no parameter documentation is needed. The description adds no param-specific detail, but with no parameters there is nothing additional an agent could need, so the baseline of 4 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 a specific verb ('Check') and defines the exact resource ('remaining flowmusic credits') plus the second datum returned ('subscription tier'). It is immediately clear what this tool does and materially distinguishes it from generic siblings like check_credits.

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 clearly implies the use case: call when you need credit balance and tier information. However, it provides no explicit guidance on when to choose this over sibling tools such as check_credits, flow_dashboard, or flow_status, nor does it state any exclusions.

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