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

Annotations already declare readOnlyHint=true, openWorldHint=false and destructiveHint=false, so the safety profile is covered structurally. The description adds only the 'today' default and the pre-regeneration rationale; it says nothing about scope of the plan, whether an empty day returns nothing, or freshness of the data.

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?

Three short sentences with the core action front-loaded, then default, then purpose. No filler and nothing that needs to be hunted for.

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?

An output schema exists, so return shape need not be explained, and the only parameter is fully documented in the schema. For a simple read-only tool this is nearly complete; only the behavior on days with no plan is unstated.

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% and the single date parameter is fully documented there, including the YYYY-MM-DD format, the ISO-datetime tolerance and the today default. The description only restates the default, adding no new format or edge-case detail beyond the schema, so the baseline of 3 applies.

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 and resource ('Read the user's plan') with a defined scope ('for a given day'). It implicitly distinguishes itself from write siblings like save_plan, but never explicitly contrasts with view_task or view_lists, which also read and could plausibly surface plan data.

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 a concrete usage context: call it before regenerating to see what is already in place. That is a clear situational cue, though it names no alternative tool or exclusion condition (e.g. that this is read-only and save_plan is the mutation counterpart).

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