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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds behavioral context beyond annotations: it discloses exactly what the output contains (monthly amounts, percent of total spending, month-over-month change) and the mutual-exclusion constraint between category_id and category_name. No contradictions.

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 compact and front-loaded: one sentence states the core purpose, a second expands on what is shown, and a structured Args/Returns section follows. Every sentence earns its place with zero filler.

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?

With no output schema present, the description appropriately explains the return values (monthly amounts, percent of total, change percentages) and all parameters. The combination of purpose, parameter constraints, defaults, and return values makes the tool fully callable by an agent.

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 carries the full burden for documenting parameters. It explains each parameter individually, including the OR relationship between category_id and category_name, case-insensitivity, and the default for months. This is exactly the meaning the schema lacks.

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 leads with a specific, specific verb+resource phrase: 'Get monthly spending trend for a specific category.' It clearly distinguishes this analytics tool from siblings like get_spending_summary or get_cash_flow by naming the exact analytical output (category trend). Full clarity.

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 clearly implies its use case — retrieving monthly trend data for a specific category — which implies the context for choosing this tool among analytics siblings. It does not explicitly name alternatives or exclusions, but the context is unambiguous enough for an agent to select it.

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