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

With no annotations, the description carries the full burden. It discloses a valuable behavioral trait: 'New days count from today on, so its streak isn't broken.' However, it omits other mutation behaviors like partial update semantics, error conditions, or permission requirements.

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, front-loaded with purpose and fields, then a behavioral note. Efficient with little waste, though the parenthetical slightly interrupts flow.

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 mutation tool with no annotations and no output schema, the description is somewhat complete but lacks important details: partial update behavior, error handling, and differentiation from update_routine. It does provide the streak behavior, which is helpful.

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 67%, so the schema documents most parameters. The description lists the updatable fields but adds no meaning beyond what the schema provides (e.g., it doesn't explain the 'kind' enum or time format). Baseline 3 is appropriate given moderate coverage.

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 states a specific verb 'Change' and resource 'habit or routine', and enumerates the fields that can be modified. It does not differentiate from the sibling tool update_routine, which could cause ambiguity, but the core purpose is clear.

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 provides a hint to get the id from list_habits, implying usage, but gives no explicit guidance on when to use this tool versus update_routine or other alternatives. The guidance is only implicit.

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