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

Annotations flag destructive and non-idempotent, and the description adds real context beyond them: the deferred-effect behavior (refills only start after a card is saved) and the consequence of omitting idempotencyKey (each call executes again), which explains the idempotentHint=false in practical terms.

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?

Three compact sentences with the action front-loaded, followed by the deferred-effect caveat and the idempotency warning in order of importance. The 'Step 6' prefix adds workflow context at negligible cost.

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 five-parameter mutation with no output schema, the description covers the key behavioral risks: timing of effect and retry semantics. Minor gaps remain regarding what happens to existing settings on overwrite and permission requirements, but the essentials for correct invocation are present.

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 only 40%, but the description clarifies the retry semantics of idempotencyKey and the purpose of threshold/amount in the refill flow. It says nothing about businessId (covered in schema) or the min/max bounds on amounts, leaving some compensation on the table.

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: turning auto-refill on/off and setting threshold and amount, framed as funding the wallet. It implicitly distinguishes from ringkit_top_up (manual funding) and ringkit_get_auto_refill (read) but never names those siblings, so differentiation relies on inference.

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?

Provides a useful precondition — it can be enabled before a card is saved, with refills starting only after a human saves one in the dashboard — but gives no explicit guidance on when to choose this versus ringkit_top_up, or on ordering relative to the other onboarding steps.

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