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

The annotations already establish that this is a non-read-only, non-destructive write operation. The description adds valuable behavioral context beyond those annotations: the first created routine automatically becomes the active routine, and routines are assembled from existing template IDs. This is a meaningful side-effect disclosure that helps agents predict consequences.

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?

Four sentences, each earning its place: the core purpose, the domain definition, the prerequisite workflow, and the important side effect. There is no filler, and the most critical identifying information is front-loaded in the first sentence.

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?

For a creation tool with 100% schema coverage, no output schema, and annotations that already signal write behavior, the description covers the prerequisites, the domain concept, and the key side effect. It is complete enough for an agent to call the tool correctly; the only minor gap is the lack of any mention of return behavior, but that is not essential here.

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 100%, so the baseline is 3. The description adds genuine semantics beyond the schema by explaining that template_ids are existing templates, that frequency means 'how many times per week to train', and that a routine cycles through workout templates. This helps an agent understand how the parameters relate to the domain model.

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 opens with a specific action and resource ('Create a new routine from existing template IDs') and immediately distinguishes this from sibling tools like create_template and create_workout by defining what a routine is. It also mentions the automatic active-routine side effect, which makes the tool's purpose unambiguous.

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?

The description gives explicit prerequisite guidance: use search_exercises and create_template first if new templates are needed. It clearly implies this tool should be used when templates already exist, which helps an agent decide when to call it versus setting up prerequisites. It could be stronger by explicitly naming set_active_routine as an alternative for changing the active routine, but the guidance is clear enough.

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