record_habit

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

The description adds value beyond the annotations by disclosing that the sync database is updated and the Marvin app reflects the change immediately. Since the annotations already establish this is a mutating, non-idempotent operation, this is meaningful extra context rather than redundancy. There is no contradiction with 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?

Two concise, front-loaded sentences with no filler. The first sentence states the primary action, and the second explains an important behavioral side effect and why it matters.

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 simple mutation tool with full schema parameter coverage, annotations covering the safety profile, and an output schema present, the description is complete enough for correct invocation. The sync-database side effect is explicitly disclosed, leaving no critical behavioral gap.

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?

All three parameters have complete descriptions in the input schema, so the baseline applies. The description does not add parameter-level detail, and the mention of updateDB=true could be slightly confusing since it is not a schema parameter. Overall, the schema carries the parameter documentation burden adequately.

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 identifies the action ('Record (or undo)') and the resource ('a habit'), making the tool's purpose immediately understandable. It does not explicitly call out sibling tools, so it stops short of full differentiation, but the verb and resource are distinct from task-oriented siblings like mark_done/unmark_done.

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 implies the tool is for recording or undoing habit entries, but it gives no explicit guidance on when to prefer it over list_habits/get_habit or how it relates to task completion tools. The core use case is inferable, but the description lacks explicit when/when-not guidance.

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