Check the credit balance

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

Annotations already convey readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds context about where credits are purchased and that the balance is consistent across platforms, which is helpful beyond annotations. It does not disclose response format, caching, or potential delays, but for this simple read operation the added context is adequate.

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?

Two short sentences with no filler. The primary meaning ('how many credits the account has') is front-loaded, and the additional context about pricing and shared balance is concise and relevant.

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 zero-parameter read-only balance checker, this description is nearly complete: it states what the tool returns and clarifies that the balance is account-wide across platforms. Without an output schema, a minor gap is that it does not specify the unit or exact return type beyond 'how many credits', but the meaning is still clear.

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, so the schema is trivially complete (coverage 100%). The description correctly avoids inventing parameters; with 0 params, it only needs to clarify the returned meaning, which it does.

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 states the tool's core function – telling the agent how many credits the account has. It is clear and unambiguous, but lacks an explicit verb like 'retrieve' or 'get' and does not directly distinguish itself from siblings such as estimate_cost or check_job.

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 when to use the tool (whenever you need the account's credit count), and the note that the same balance serves the website and this server adds useful context. However, it offers no explicit when-to-use/alternatives guidance or exclusions.

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