get_month_summary

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

With no annotations the description carries the full burden, and it discloses two genuinely useful traits: expenses are returned as positive values (sign convention) and the closing balance is real when the month is closed but projected otherwise. It omits permission requirements and behavior when a month has no data, but the disclosed semantics exceed what the schema provides.

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?

Front-loaded with the core purpose, followed by a dense but necessary enumeration of return fields, the sign convention, and the detail-tool routing. Three sentences, no filler; the field list is long but justified because there is no output schema.

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?

Since no output schema exists, the description does the work of enumerating the returned figures and their real-vs-projected semantics, which is the key information an agent needs. Edge cases (empty month, invalid range errors) are left unstated but are partly covered by the schema's min/max constraints.

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?

Both parameters (year, month) are fully documented in the schema, including the 1-12 range for month. The description adds no param-level detail beyond that, 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?

States a specific resource (monthly totals) and enumerates exactly which totals are returned: income, fixed expenses, variable/budget expenses, savings, extras, savings withdrawals, and opening/closing balances. It also names the sibling tool (list_movements) that covers the detail case, so an agent can tell it apart from the other list_* tools without opening a schema.

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?

Explicitly routes the agent: use list_movements to see the underlying detail, implying get_month_summary is the aggregate view. It does not address when to prefer this over get_annual_overview or list_months, but the use context is clear and actionable.

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