Grok monthly credit units (secondary)

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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, openWorldHint), but the description adds real behavioral context: the data comes from an unofficial billing endpoint, it is non-authoritative ('SECONDARY / optional'), and it does not gate the weekly limit. It stops short of mentioning rate limits, auth needs, or response shape.

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 sentences, no filler. The 'SECONDARY / optional' qualifier and the routing instruction are front-loaded, and the qualifying clause about the weekly limit follows immediately.

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 tool with annotations covering safety, the description supplies everything needed: what it returns, that it is non-authoritative, and when to use get_budget instead. No output schema is present, yet the returned fields are still described.

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?

Zero parameters, so the baseline is 4. The description goes slightly beyond by naming the fields the tool surfaces (monthly_limit, used, billing period) and noting the underlying call omits format=credits, which is extra meaning the empty schema cannot convey.

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+resource (monthly credit units) and enumerates the data returned (monthly_limit, used, billing period). It also names the sibling it is subordinate to, so an agent can distinguish it from get_budget without opening either 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?

Explicitly labels itself 'SECONDARY / optional', states what it does NOT gate (the weekly Grok Build limit), and routes the agent to 'prefer get_budget'. Both the when-not and the alternative are spelled out.

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