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

With no annotations present, the description carries the full behavioral burden and does well: it states the resource is 'Always personal' and discloses the concrete Caddie defaults (habit: 30 minutes at 07:00 on weekdays; routine: 45 minutes at 12:30 every day). It does not cover permissions, duplicate handling, or side effects, so it falls short of complete.

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 dense sentences that front-load the two kinds before adding the disambiguation and defaults. The parentheticals earn their place, though the sentence is slightly packed and could be split for easier scanning.

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 a 5-parameter mutation tool with no annotations and no output schema, the description covers semantics, defaults, the personal-only constraint, and sibling disambiguation. Error or duplicate behavior is absent, but the major calling context is present.

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 already 80%, so the schema documents most parameters. The description adds genuine meaning beyond the schema by tying specific default values to kind (default minutes, times, and days per habit/routine), which the schema only partially captures via 'default habit'.

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 opens with a specific verb and resource ('Add a habit… or a routine') and immediately defines what each kind is: a habit is ticked off with a streak, a routine is planned calendar time. It also disambiguates from the sibling create_routine by calling out that agent routines are handled separately.

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 gives clear context for choosing between the two kinds and explicitly routes agent-routine creation to create_routine. It lacks explicit exclusions against update_habit or update_routine, but for a creation tool the distinction is well covered.

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