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

Annotations already declare non-readOnly, non-destructive, non-idempotent, closed-world, so safety is covered. The description adds genuinely useful behavior the annotations cannot convey: date-inference rules, the 'no future dates' constraint, and the warning that 'ended today' alone does not supply a start date.

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?

It is short and front-loads the purpose, and most sentences carry real information. However, terse fragments like 'Edits: update_cycle(date) when offered' and 'Voice without update_cycle' are cryptic and require re-reading, which undercuts the structure.

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?

An output schema exists, so return values need not be explained. For a temporal logging tool with only two parameters, the description covers the decision path (create vs edit vs resume) and the inference rules an agent needs; only edge cases like duplicate same-day entries are unaddressed.

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 schema already documents format and 'omit if active,' giving a baseline of 3. The description goes beyond it by specifying when to set started_on=today versus inferring it, and how to derive ended_on from a stated end or duration.

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 opening sentence gives a concrete verb+resource+scope: 'Log a new period or resume one ended today.' It also implicitly separates the create path from the edit path by naming update_cycle, so an agent can distinguish it from sibling mutation 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?

It explicitly routes edits to update_cycle and notes list_cycle is unnecessary, and gives the specific condition under which log_cycle is correct (new start, or a period that ended today). The guidance is clear but phrased conditionally ('when offered', 'Voice without update_cycle'), which leaves some interpretation to the agent.

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