update_habit

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

Annotations already declare this as a non-destructive, idempotent, closed-world write, so the bar is lower, yet the description still adds substantive behavior: empty fields are preserved (true partial-update semantics), notes are wholesale replaced rather than appended, and dates must be YYYY-MM-DD and non-future. The notes-replacement warning is exactly the kind of data-loss nuance annotations cannot express.

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 tightly packed sentences with the core verb/scope front-loaded, then invocations rules, then the notes caveat, then format constraints. The quoted user phrasings earn their space by mapping natural language directly onto parameters.

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?

Return values need not be explained since an output schema exists, and the main update workflow is fully described. The gap is the four undocumented habit-type-specific fields, which an agent could misuse given 0% schema coverage, though they are optional and niche.

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 description coverage is 0% across 10 parameters, so the description must carry the full burden; it covers habit_id's source, notes replacement semantics, status/end_date via example, date formatting, and frequency. Four parameters — habit_type, smoking_years, drinks_per_week, cigarettes_per_day — get no explanation at all, leaving an agent to guess their meaning and units.

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 ('correct'/'update') and resource ('a recorded habit'), making clear this operates on an existing record rather than creating one. The 'habit_id from get_habits' clause anchors it against get_habits, but the sibling it most needs to be distinguished from, record_habit, is never named explicitly.

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 when-to-use guidance through worked examples ('I quit in September' = status former + end_date; 'now twice a week' = frequency) and the key invocation rule 'pass only the fields to change (empty = keep)'. What is missing is any exclusion — it never says when to use record_habit instead or what to do if the habit doesn't exist.

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