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

Annotations already declare readOnlyHint=true and destructiveHint=false, and the description adds substantial behavioral detail: the >20% threshold, the 6-month comparison window, the minimum historical occurrences requirement, empty-list behavior when nothing qualifies, and ordering by largest deviation. This goes well beyond the annotation safety profile.

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?

The description is three sentences with zero waste. The core anomaly rule is front-loaded, followed by the exclusion condition and output ordering behavior. Every sentence carries essential, non-redundant information.

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 zero-parameter, read-only analysis tool with an output schema, the description is fully complete. It explains the detection rule, prerequisites, edge cases, ordering, and empty behavior. There is no missing information needed to invoke or interpret the result.

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 has zero parameters, so schema description coverage is 100% and no parameter documentation is needed. The description appropriately focuses on the tool's filtering semantics rather than parameters, matching the baseline for a no-parameter tool.

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 exactly what the tool does: it identifies active recurring expense bills whose latest posted occurrence this month exceeds the 6-month average by more than 20%. It gives concrete examples (rent, electricity), clear exclusion criteria, and output ordering, making it distinctly recognizable among sibling analytics tools.

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?

The description provides clear context for when to use it — for surfacing unusually high recurring bills in the current month — and defines qualifying conditions (active recurring expenses, at least 2 historical occurrences). It does not explicitly name alternative tools or state when not to use it, so it misses the full 5.

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