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

Annotations only say destructiveHint=true and idempotentHint=false; the description adds the billing mechanism (daily accrual from wallet), the credit-source restriction, the refusal condition on downgrade, and the retry/idempotency consequence ('without one, each call executes again'), which is consistent with idempotentHint=false. That is substantial context an agent cannot get from the annotations.

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?

Dense but front-loaded, with the verb first and the pricing/precondition detail after; every clause carries actionable information. The nested parentheses in the pro clause make it slightly harder to scan than it needs to be.

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 billing-affecting mutation with no output schema and only three parameters, this covers cost, credit eligibility, refusal semantics, and retry behavior. What's still unstated is whether the switch takes effect immediately, whether it is prorated, and what happens to existing documents on a permitted downgrade.

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 67% and both businessId and idempotencyKey already carry descriptions. The description's real contribution is giving meaning to the bare 'tier' enum by spelling out what starter and pro actually grant and cost, plus reinforcing that idempotency requires the caller-supplied key.

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 ('Switch the knowledge tier') and immediately defines the two enum values with their concrete capacities and costs, so an agent knows exactly what this does versus siblings like ringkit_patch_knowledge or ringkit_get_knowledge_usage.

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 the decisive preconditions for each tier: pro needs $5 of paid credit (trial credit excluded) and bills daily; starter is refused while usage exceeds its limits. It doesn't name an alternative tool, but no sibling offers tier switching, so the guidance is effectively complete; the only gap is no explicit statement of when to prefer one tier.

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