budget_vs_actual

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

The annotations already declare readOnlyHint=true, so the agent knows this is a safe read operation. The description adds the behavioral trait of highlighting over/under-budget categories, which is useful context beyond the annotation. However, it does not disclose specifics like whether the result is a summary or detailed breakdown, or if default behavior (current month) is implied. This adds some value but not extensive detail.

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 two sentences, front-loading the core purpose and immediately adding the distinguishing highlight outcome. Every word earns its place; there is no fluff or repetition.

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?

Given the tool's relative simplicity, two optional parameters, and the read-only annotation, the description is fairly complete. It explains what the tool does and the key output (highlights categories). The absence of an output schema is mitigated by the clear statement of what is returned (comparison and highlights). The only minor gap is not detailing the return format (e.g., table vs list), but this is not critical.

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 description coverage is 100%, meaning both parameters ('group' and 'month') are already documented with meaning. The description implies that 'month' is a filter and 'group' may be a category filter, but it doesn't add syntax or default behavior beyond the schema's 'Defaults to current month'. With full schema coverage, the baseline is 3, and the description provides marginal additional context.

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 clearly states a specific verb ('Compare') and resource ('budgeted amounts versus actual spending'), with a defined scope ('for each category in a given month') and a distinguishing outcome ('highlights over-budget and under-budget categories'). This is distinct from sibling tools like 'get_budget_month' or 'spending_by_category', so an agent can easily tell them apart.

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 indicates when to use this tool (to compare budget vs actual for a month) and the outcome it provides. However, it does not explicitly state when not to use it or mention alternatives; although the sibling list includes related tools like 'get_budget_summary' or 'spending_by_category', no exclusions are given. This is clear context but lacks alternative routing.

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