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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the read-only claim is partly redundant, but the description adds genuinely new context: a connected Phorme account is required and weights are returned in pounds. That auth prerequisite and unit convention are not derivable from the structured fields, which lifts it above the annotated baseline.

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?

Front-loaded with the trigger condition and example, then constraints and the alternative — logical order with little waste. The 'reads only and changes nothing, including the plan' clause is slightly redundant against the annotations, keeping it short of perfect.

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, yet the description still summarizes contents. With auth need, unit convention, usage trigger, and sibling routing all present, an agent has everything needed to call this correctly.

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% and the single 'days' parameter is fully documented there (range, default 7), so the schema carries the burden. The description only implies a forward-looking window ('today or the coming days') without adding constraints or format detail beyond the schema, matching the baseline for high-coverage schemas.

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+resource (get planned Phorme sessions) and immediately scopes what a session contains (exercises, sets, reps, auto-set loads). It also explicitly routes away from the sibling preview_workout_import for non-plan sessions, so an agent can distinguish it 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?

Gives an explicit trigger ('when the user asks what their Phorme plan has for today or the coming days'), a concrete example utterance, and an exclusion ('Do not change the loads; for a different session, build one with preview_workout_import'). This is the when/when-not/alternative pattern in full.

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