update_cycle

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint. The description adds useful behavioral context beyond the annotations, such as the effect of passing null for ended_on (clears the date and marks active) and the selector resolution behavior. It does not contradict the 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 well-structured with a main statement, a 'Common uses' list, and a 'SELECTOR' paragraph. Each sentence adds value (use cases, selector rules, null handling) without redundancy or fluff. It is appropriately sized for the complexity.

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?

The tool has an output schema, so return values are documented elsewhere. The description covers the action, use cases, selector logic, and parameter behaviors, making it self-sufficient for an agent to decide when and how to call it. No critical information 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?

Schema coverage is 100%, so the baseline is 3. The description repeats the parameter explanations already present in the schema (e.g., id as alternative to date, date resolving only when a single match exists). It does not add new semantic details beyond what the schema already provides, so it stays at baseline.

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 the verb 'Update' and the resource 'period record', and it lists common use cases (correct dates, add/clear end date). It is easily distinguished from sibling tools like log_cycle, list_cycle, and delete_cycle by the explicit update action.

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 provides concrete examples of when to use the tool ('my period ended on the 9th not the 8th', 'I'm still on my period'), and it explains the selector rules (pass id or date, exactly one required, error if multiple matches). This gives clear guidance on when and how to invoke without needing to infer.

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