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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so safety is covered structurally; the description reinforces this with "Nothing changes" and adds genuinely new context: the result is ordered "best first" and this tool is the read step before the mutating swap_exercise. It stops short of describing result volume or whether an empty list is possible.

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 sentences, front-loaded with the trigger, then the effect and ordering, then the routing alternatives. Every clause carries information an agent needs; nothing is repeated from the title or annotations.

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?

The tool is low complexity, has an output schema so return values need not be explained, and the description covers purpose, safety, ordering and alternatives. The only real gap is the undefined slot/sessionId semantics, which matters because it is a required input with zero schema documentation.

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 0%, so the schema supplies only types with no meaning, and the description must compensate. It does name both parameters ("by sessionId and slot") and situates slot as a position within a session and week, which adds some meaning, but it never defines the slot value format or whether sessionId is the current session or any session.

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 ("Lists") and a precisely scoped resource: swaps that train the same movement in that slot and week, best first. The scope is narrowed further by "in a session" and "that slot and week", so it is clearly distinguishable from show_exercise and get_session without opening any 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?

Explicit trigger conditions are given with concrete examples ("a busy machine, a sore joint, missing kit"), an explicit when-not ("Do not use to explain how an exercise is done; use show_exercise"), and an explicit follow-up alternative ("swap with swap_exercise"). Both the exclusion and the downstream action name the sibling tools directly.

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