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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered; the description adds the useful disclosure that the response includes policy and runtime enforcement state, not just balances. The units convention (microusd = integer millionths of USD) is genuinely valuable behavioral context absent from any structured field.

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, zero waste, front-loaded with what is read, and the unit convention follows immediately. Every sentence earns its place.

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 output schema and no parameters, the description carries the burden of describing return contents, and it does enumerate the key fields including policy and runtime enforcement. It stops short of stating account/scope assumptions or whether the wallet is per-organization, which would fully close the gap.

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 the baseline is 4 and there is nothing to document. The description instead spends its second sentence on output-unit semantics, which is a sensible use of space given the absent schema.

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 (Read) and a specific resource (prepaid wallet funds) plus the exact data returned: available, reserved and total funds, policy, funding availability and runtime enforcement. It is distinguishable from siblings like list_payments or list_balance_activity, though it never names or contrasts with get_billing_policy, which overlaps conceptually.

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?

Usage is only implied: an agent can infer this is the balance-checking tool, but there is no explicit when-to-use statement and no routing against near-neighbours such as get_billing_policy, check_entitlements or list_balance_activity. Nothing is misleading, but the agent must infer the choice.

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