get_credits

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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior, so the safety profile is covered structurally. The description adds genuinely new context: the required billing:read scope and the fact that credits are a shared workspace wallet, which changes how the returned figure should be interpreted.

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 dense sentences with the core answer front-loaded and no filler. Every clause carries information the agent needs: balance components, wallet semantics, cost, and auth scope.

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?

With no parameters, no output schema, and annotations covering safety, the description is close to complete—it even enumerates the balance fields an agent will receive. It stops short of describing the response shape or formatting, which is the one gap given the absence of an output schema.

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 takes zero parameters, so there are no parameter semantics to document and the schema coverage question is moot. Baseline 4 applies; no meaning is added or needed beyond the empty object.

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 ('Get the authenticated user's posterly AI credit balance') and then enumerates exactly what the balance comprises: available spend, remaining monthly allowance, purchased pack balance, plan tier, and reset timing. An agent can distinguish this from subscription-management siblings like get_subscription purely from the text.

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?

Gives clear context for when this is the right call (read-only, spends nothing, requires billing:read scope) and clarifies the shared-workspace semantics so callers don't mistake it for a personal balance. It stops short of naming an alternative sibling or explicitly stating when not to use it.

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