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

Annotations already declare readOnlyHint=true, idempotentHint=true and destructiveHint=false, so the safety profile is covered without description help. The description adds real behavioral value by explaining the computed `next_routine` semantics (today's routine in a fixed-day plan vs. the next in a rotation), which is logic an agent cannot infer from annotations alone.

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, zero waste: the usage trigger is front-loaded, then the return content. Every clause carries information the agent needs to decide to call it and to interpret next_routine.

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 values need not be enumerated, and the description instead covers the one non-obvious semantic (how next_routine is derived). For a no-argument read tool this is complete: an agent knows when to call it and how to read the answer.

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 tool takes zero parameters, so the baseline is 4 and there is no parameter meaning the description needs to supply. It neither overstates nor misdescribes any input.

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 uses a specific verb and resource ('Returns the active plan, its routines and exercises') rather than restating the name. It also implicitly distinguishes itself from the sibling get_routines by scoping the result to the *active* plan plus a next_routine decision.

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 an explicit, natural-language trigger ('when the user asks what to train today or next, or about their current training plan'), which is exactly the routing signal an agent needs. It stops short of naming an alternative or exclusion (e.g., when to prefer get_routines or get_workout_history instead), so it is clear context but not full when/when-not guidance.

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