record_habit

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

Annotations already signal a mutating, non-idempotent operation. The description adds a useful side effect: it updates the sync database (updateDB=true) so the Marvin app shows the change immediately. This is beyond the structured hints, though the cryptic 'updateDB=true' parenthetical introduces a name not present in the input schema.

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 sentences, with the primary action front-loaded and no filler. The second sentence earns its place by disclosing the sync side effect, though the parenthetical updateDB=true is unnecessarily cryptic and could be simplified.

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?

This is a simple tool with full schema coverage and an output schema, so the description does not need to restate return values. It covers the action and the key side effect, leaving only the when-to-choose guidance under-specified.

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 100%, so the baseline is 3 even without description-level parameter detail. The description does not add meaning to habit_id, undo, or value; its only parameter-adjacent mention, updateDB=true, is not an actual input parameter and could confuse rather than clarify.

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 first sentence states a specific verb and resource: 'Record or undo a habit check-in.' This clearly identifies the operation and distinguishes it from task-focused siblings like mark_done or unmark_done. However, it does not explicitly contrast itself with sibling tools, so it stops short of full differentiation.

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 no explicit guidance on when to use this tool versus alternatives such as list_habits/get_habit for reading habits or mark_done/unmark_done for tasks. The 'undo' option hints at one usage scenario, but there is no when-to-use or when-not-to-use guidance.

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