category_trends

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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds a small behavioral cue ('Identifies increasing/decreasing patterns') but does not explain how trends are computed, what aggregation is used, or what the output looks like. It adds some value but remains thin.

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 short sentences with no filler. The primary action is front-loaded, and the second sentence adds analytical intent. Every word 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?

This is a simple read-only tool with two optional parameters, and the schema covers both. The description suffices for basic invocation. However, with no output schema, it could have briefly described the result shape or what 'trends' means in the response; its absence is a minor gap rather than a critical one.

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 100% – both 'months' and 'category' have descriptions, including the fallback behavior of 'category' when omitted. The description itself adds no parameter-level information beyond the schema, so the baseline of 3 applies.

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 clear verb and resource: 'Show spending trends for a category across multiple months.' It distinguishes this from simple spending breakdowns like spending_by_category by emphasizing 'trends' and 'patterns.' However, it does not explicitly name any sibling alternative, so it stops short of a 5.

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 implied rather than stated: an agent can infer the tool is for analyzing category spending patterns over time. There is no explicit when-to-use guidance, exclusions, or comparison with alternatives like spending_by_category, spending_projection, or monthly_summary.

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