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

Annotations already declare readOnly/idempotent/non-destructive, yet the description still adds real behavioral context: tasks from spheres hidden with 'Hide from my day' are excluded from both the task list and the week's planned-vs-done, their count surfaces as hidden_from_day, the in-app Dashboard still counts their completed items, and get_tasks still lists them. That cross-surface discrepancy is exactly the kind of subtlety an agent would otherwise get wrong.

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?

The core return contents are front-loaded in the first sentence and the sibling routing and defaults follow, so nothing is buried. It is a dense single paragraph with some mild redundancy ('reading a day without showing it' followed by 'reviewing how a day went, or answering a question about it') that could be tightened.

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?

There is no output schema, but the description effectively documents the return shape (task ordering, carried-over tasks, streaks, weekly planned-vs-done, hidden_from_day), plus the filtering caveat and the date default. For a one-parameter read tool, an agent has everything needed to call it correctly and interpret the result.

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?

With one parameter at 100% schema coverage, the schema already carries the format (YYYY-MM-DD pattern). The description adds meaning the schema does not: the date is optional and omitting it defaults to the user's today, which is the only real semantic ambiguity in the call.

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 names a specific verb and resource (a single read that returns a day's brief) and enumerates exactly what comes back: the day's tasks in display order, tasks left open the day before, repeating tasks with streak, and planned-vs-done for the week. It also explicitly distinguishes itself from show_day, so an agent can choose between the two without opening either 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 states both sides of the routing decision: 'Fits for reading a day without showing it: reviewing how a day went, or answering a question about it' versus 'When the user wants to see or plan their day, show_day fits.' It also gives the default behavior ('Omit date for the user's today'), so no inference is required.

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