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

With no annotations, the description carries the full burden. It implies a read-only check and adds genuinely useful domain context (1 credit = US$0.0001), but it never explicitly states that the call is side-effect free, nor does it describe what the response looks like or any rate limits.

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, front-loaded with purpose, then the credit conversion, then the next action. Every sentence carries information the agent can act on; nothing is wasted.

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 simple read with no output schema and fully documented parameters, the description covers purpose, units, and next steps adequately. The only missing piece is what happens when account_key is not supplied, given it is an optional parameter.

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?

Schema coverage is 100% and the single account_key parameter is fully documented in the schema, including the Bearer alternative, so the schema does the heavy lifting. The description adds nothing about the parameter, and notably does not explain behavior when account_key is omitted (0 required params), which is the one gap the schema leaves open.

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?

States a specific verb and resource: checking how many credits an account has left. This is unambiguous and clearly distinct from siblings like pricing or deposit_status, so an agent can select it without opening the schema.

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 line "Next: call create_deposit if the balance is low" gives an explicit follow-up action tied to a condition, which is useful routing. It does not, however, address when not to call it or clarify its relationship to pricing/deposit_status.

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