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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorld=false, but the description adds substantial behavior beyond them: the result cap ('up to five'), the filtering rule (same kind, equipment-allowed), the per-item demo link, and a disclosed fallback ('says so when it has to offer the nearest kind instead'). 'Changes nothing, including any saved plan' sharpens the read-only guarantee with a concrete reassurance about side effects.

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 dense sentences with no filler, and the trigger conditions are front-loaded before the return behavior and the exclusion. It is slightly long for the payload, but every clause carries distinct information, so the sizing is defensible rather than padded.

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 explanation is not required, and the description stays complete for the remaining gaps: trigger conditions, fallback behavior, and the safety exclusion. An agent has everything needed to decide whether to call it and what the caller will receive.

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%, so the schema already documents all three parameters including the reason enum and the available_equipment example array, making 3 the baseline. The description reinforces the preference/busy/equipment framing but adds no syntax, format, or constraint detail the schema lacks.

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 ('a replacement for one exercise') and enumerates the exact conditions that trigger it (missing equipment, busy station, wanting a different option) with a concrete example ('no cable machine for cable rows'). Clearly distinguishable from every sibling, all of which are read/save/preview tools rather than substitution finders.

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 both when-to-use (the three triggering reasons plus the cable-row example) and an explicit when-not-to-use exclusion ('Do not use it to work around pain or injury'). This is the strongest form of routing guidance and covers the main misuse case for a fitness-tool substitution helper.

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