check_balance

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

The description notes each SMS consumes 1 credit, adding behavioral context beyond the tool name. Without annotations, it provides relevant safety information (read-only, non-destructive) and explains the credit consumption model.

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 concise sentences convey purpose, consumption relationship, and usage recommendation with no wasted words. The key action 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 parameterless tool with no output schema, the description covers the core functionality and usage context. It could mention the return format (e.g., number of credits) but remains adequate for selection and invocation.

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 no parameters and 100% schema coverage, the description adds no param details but doesn't need to. The baseline of 4 is appropriate as the description sufficiently clarifies the tool's purpose.

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 states the tool checks the balance of available SMS credits, specifying the resource (SMS credits) and the action (consulta). It distinguishes itself from sibling tools like send_sms or verify_phone, which have different purposes.

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 explicitly advises using this tool before sending messages to verify balance, providing clear when-to-use guidance. It does not exclude alternative uses, but no sibling tool duplicates this functionality.

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