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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description does add one genuinely useful behavioral fact: the result may indicate that today has not been designed yet, which is an empty-state the agent should anticipate. It says nothing about pagination, freshness, or return shape beyond that.

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?

One compact sentence with no filler, and the two possible outcomes are stated up front. Slightly awkward grammar ('or that today is not designed yet') but nothing is wasted.

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?

With no output schema and a read-only annotation profile, the description does just enough by flagging the not-yet-designed case. It still leaves the shape of a returned session unspecified, which an agent selecting and parsing this tool would benefit from knowing.

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 100% and the single optional `today` parameter is fully documented in the schema, including the 05:00 cutoff rule and the omit-if-unknown instruction. The description contributes no parameter meaning at all, so the baseline 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?

The description identifies the resource (today's training sessions as the coach designed them) but is phrased as a noun fragment with no verb, so it reads more like a title restatement than a defined action. It also does not differentiate itself from nearby siblings such as schedule, edit_schedule, or morning_check_in.

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?

There is no explicit when-to-use guidance and no named alternative. An agent must infer on its own whether this is the right tool versus schedule or morning_check_in, and no prerequisites or exclusions are given.

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