create_custom_food

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

Goes well beyond the annotations (readOnlyHint=false, openWorldHint=true) by disclosing the subscription gate, the non-obvious PUT-instead-of-POST method, the string encoding quirk, per-serving absolute amounts, and the returned `foodId`/`servingId`. These are exactly the behaviors an agent cannot infer from structured fields.

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?

Dense but front-loaded, leading with the subscription requirement and payload shape. The one flaw is the redundant tail 'Needs Connect+' which restates the opening prerequisite, a sentence that doesn't earn its place.

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 nested-object mutation tool with no output schema, the description supplies everything needed: prerequisite, method, complete payload contract, encoding, and the return identifiers for chaining. Nothing material is missing.

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?

With 0% schema description coverage, the description fully compensates by enumerating every `CustomFoodInput` field with defaults (`servingUnit = "G"`, `servingSize = 100`) and clarifying that values are per ONE serving, absolute (not %DV), and serialized as strings. This adds meaning the schema alone does not convey.

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 name states a specific verb+resource (create a custom food) and the description reinforces it via the endpoint `/nutrition-service/customFood` and 'Returns the stored food'. It also differentiates from siblings by naming `logFood` as the consumer of the returned IDs. The prose itself never uses the word 'create', leaning on the name for the core verb.

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?

It states a real prerequisite ('Requires a Garmin Connect+ subscription (check with has_connect_plus)') and points to `logFood` as the downstream tool. However, it never frames when to reach for this vs. `update_custom_food`, `get_custom_foods`, or `quick_add_food`. Usage is implied rather than explicitly routed.

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