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

The annotations already declare this is a non-readonly, non-idempotent, non-destructive mutation, so the safety profile is covered without description help. The description adds only the sentinel behavior '0 turns it off' for one field; it never says whether unspecified preferences are preserved (partial update), whether confirmation is needed, or that changes persist immediately. Adequate but thin on behavior beyond 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?

A single sentence with no filler, front-loaded with the usage trigger and then the two affected settings. Slight verbosity in the 'Use this when the user wants to' framing, but nothing wasted.

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 mutation tool with no output schema and 0% schema description coverage, the description covers both fields at a high level but omits partial-update semantics (both params optional), whether values are validated or rejected, and any confirmation/persistence note. Reasonably complete for a two-option settings setter, but key mutation behavior is left implicit.

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%, so the description must carry the load. It usefully documents the unit for lowStockDefaultGrams ('grams') and the sentinel value ('0 turns it off'), but adds nothing about currencySymbol format/length or the fact that both parameters are optional and can be sent independently. It covers the meaning of one parameter well and leaves the other and optionality gaps unaddressed.

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 names a specific verb (change) and the exact resources affected (currency symbol, default low-stock warning in grams), which clearly separates it from the read-only sibling my_account. It stops short of explicitly naming that sibling or any other alternative, so it is clear but not maximally differentiated.

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?

It states a clear trigger condition: 'Use this when the user wants to change the account's currency symbol or its default low-stock warning.' There is no guidance on when not to use it, no prerequisites (e.g., ownership/permissions), and no named alternative for viewing preferences, so it lands at clear context without exclusions.

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