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

Annotations already declare the non-read-only, non-idempotent, non-destructive profile; the description goes further by disclosing the ongoing side effect (a record is generated on every due day) and the immediate-write case when startDate is today. It stops short of stating the failure mode for a past start date or how generated records relate to delete_recurring_expense.

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 sentences, front-loaded with the core behavior and followed by the key timing constraint. No filler and nothing redundant to the structured fields beyond a brief enum restatement.

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?

For an 8-parameter creation tool, the description covers the essential behavior, the timing constraint, and the immediate-effect edge case, while annotations carry the safety profile and an output schema handles return values. Remaining details (endDate interaction, categoryId sourcing) are fully documented in the schema.

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?

With 100% schema coverage the baseline is 3, but the description adds real meaning beyond the schema for startDate: the past-date prohibition and the "today means the first record is added immediately" consequence, which the schema only implies with "today or later." The enumerated frequency values are restated from the enum, adding no new information.

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 verb and resource ("Creates a recurring expense") plus the defining behavior that separates it from create_record: it "adds a record automatically on every due day" per a named frequency. An agent can distinguish it from the one-off record tools and from update_recurring_expense 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?

Gives concrete usage constraints: the start date cannot be in the past, and a start date of today triggers an immediate first record — both of which affect when an agent should call it. It does not explicitly name alternatives (e.g. create_record for one-off entries), so routing is implied rather than stated.

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