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

Annotations already declare readOnlyHint=false, destructiveHint=false and idempotentHint=false, so the safety profile is covered. The description adds nothing beyond that: it does not say whether omitted notification types are left unchanged or reset, whether the update merges or replaces, or what permissions are required — the most important behavior for a settings mutation.

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 no filler or redundancy. It is efficient, though arguably under-specified rather than optimally concise given the tool's complexity.

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, a nested object parameter, and zero required fields, the description should clarify merge/partial-update semantics and the effect of omitted fields. It leaves all of that to inference.

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 50%: 'types' is documented as a partial map, but low_balance_threshold has no description. The description names both concepts but adds no semantics (e.g., currency units for the threshold, merge semantics for types) beyond what the schema already conveys, so it does not compensate for the coverage gap.

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 (updates) and resource (notification toggles and low-balance threshold), which is more precise than the title. It implicitly contrasts with the sibling get_notification_preferences (read vs write) but never names it or any alternative explicitly.

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?

No guidance on when to use this versus get_notification_preferences, no mention that a partial map is acceptable, and no prerequisites or preconditions stated. The agent must infer usage from the verb alone.

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