Budget summary

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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is established. The description adds meaningful context about what the summary contains: category-level spending and a previous-month comparison. No contradiction with 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?

The description is a single front-loaded sentence that conveys purpose, grouping, comparison behavior, and the optional parameter format without any 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 only one optional parameter, a high-coverage input schema, an output schema present, and annotations covering safety, the description provides everything an agent needs to invoke the tool correctly. No essential context is missing.

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 schema already documents the month parameter fully with a regex pattern, a description, and the default behavior. The description repeats the YYYY-MM format and optionality but adds no meaning 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 uses a specific verb ('Summarises') and identifies the resource ('spending for a month by category'), including the previous-month comparison. It is clearly distinct from siblings like get_household_summary, though it does not explicitly name any alternative.

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 gives useful invocation context: the month is optional, formatted as YYYY-MM, and defaults to the current month. However, it does not state when to use this tool over alternatives such as get_household_summary or list_bills, leaving selection guidance implicit.

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