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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered. The description adds real value by showing the exact output shape ('Rp' prefix, '.' thousands separator, no decimals), but it is silent on rounding, negative amounts, and whether fractional input is truncated.

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?

A single front-loaded sentence with an inline example that does the explanatory work. No filler, no restatement of the title, and the example is placed exactly where it clarifies the expected output.

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 trivial one-parameter formatter with no output schema, the sample output string covers what an agent needs to call it and interpret the result. The only shortfall is unstated edge-case behavior (decimals, negatives) for the undocumented amount parameter.

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 description coverage is 0% for the single parameter 'amount', and the description does not compensate: it does not say whether the value is a plain number, whether decimals are allowed, or how fractions are handled. The only hint is that the input is 'a number', which is already in the 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?

The description states a specific verb and resource ("Format a number as Indonesian Rupiah string") and includes a concrete output sample (Rp125.000), so the transformation is unambiguous. It does not name the inverse or linguistic siblings (parse_rupiah, terbilang_rupiah), so differentiation relies on the tool name alone.

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 converts a numeric amount into a display string, but the description never states when to prefer it over parse_rupiah (the reverse direction) or terbilang_rupiah (spelled-out amounts). No exclusions or preconditions are given.

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