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

The annotations already declare readOnlyHint=true, destructiveHint=false, so the read-only nature is covered. The description adds the meaningful behavioral detail 'Defaults to today' and describes the scope as a single day, which is useful beyond the 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 short sentences earn their place, with the core action first and the practical usage context second. No filler or redundancy beyond what schema already contains.

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 tool with one optional parameter fully documented in the schema, annotations covering safety, and an output schema present, the description provides enough operational context with the 'before regenerating' hint. Nothing an agent needs is missing.

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?

The input schema already documents the only parameter completely with format, accepted datetime form, date-component behavior, and default. Since schema coverage is 100%, the description doesn't need to add much; it only confirms the default. Baseline 3 is appropriate.

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 ('read') and resource ('the user's plan for a given day'), which clearly distinguishes it from siblings like set_daily_plan (write) and view_lists/view_task (different resources). It is immediately obvious what the tool does without needing the schema.

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 gives explicit usage context with 'Useful before regenerating so an agent can see what is already in place.' This tells the agent when to invoke it. It doesn't explicitly list alternatives, but the sibling set_daily_plan implies the write counterpart, so the guidance is clear if not exhaustive.

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