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

With no annotations, the description carries the burden and does meaningful work: it discloses a paid call ($0.02 USDC on Base), the return shape (3-5 alternatives with prescriptions and stop signs), and a safety disclaimer ('physio-informed, not medical advice'). It omits payment/auth mechanics and any rate limits, so it is strong but not complete.

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?

Purpose and cost are front-loaded, which is good, but the trailing keyword block ('Gym, home gym, CrossFit, functional fitness') is SEO filler that adds no invocation value for an agent.

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 no annotations, the description does cover the essentials an agent needs: inputs with examples, output volume and content, cost, and a medical disclaimer. The main gap is the undocumented 'equipment' parameter and the absence of payment/auth details.

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 0%, so the description must compensate. It explains 'movement' and 'limitation' with useful examples, but never mentions the third parameter 'equipment' (defaulting to null), leaving that input undocumented in both schema and description.

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 (substitute an exercise) with concrete input examples (barbell back squat + knee pain) and a defined output (3-5 safe alternatives with prescriptions, cues, stop signs). It is clearly distinguishable from siblings like generate_workout or coach_programme, which are not injury-driven substitution.

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?

Implies the triggering condition well: use it when you have a movement plus an injury/limitation and need safer alternatives. It does not explicitly name a sibling tool or state exclusions, so it stops short of full routing guidance.

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