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

The annotations already declare readOnlyHint=true, and the description reinforces this with the word 'Check'. It adds context beyond annotations by noting the tool is free and by clarifying the credit accounting relationship with submit_transcripts_job (1 credit per video). This is useful behavioral context, though it does not discuss output format or failure modes.

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 cover purpose, cost, and two concrete use cases. There is no filler, and the primary action is front-loaded. Every sentence adds value.

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, parameterless tool with no additional configuration, the description covers all necessary context: what it does, when to use it, and how credit usage relates to submit_transcripts_job. The output schema is present, so the return value format does not need to be described in the text. 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 tool has zero parameters, and the schema is fully clear with an empty object. The description adds no parameter information because none is needed; this is the appropriate baseline for a parameterless tool.

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 a specific action and resource: 'Check the remaining credit balance of the API key.' It is unmistakably distinct from the sibling tools, which all concern transcripts, videos, or channels, so an agent can identify this as the credit balance tool without ambiguity.

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 gives explicit usage conditions: use it when the user asks about remaining credits, or before submit_transcripts_job to confirm a large batch fits. It also mentions the alternative context of submitting a job and the credit cost per video, making the decision clear.

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