# MCP use case: the tool asks the user > A tool route can stop in the middle of a call and ask the person at the client a question, through MCP elicitation, then carry on with the answer. The shop's `exchange_item` asks which size to send; if the user closes the form, nothing changes and the result says so. In the field test, both elicitation cases passed in every run. **Cargo feature:** [`ai`](../build-features.md) · **Example:** [`examples/agents/mcp-shop`](https://github.com/pmsudhi/cameleer/tree/main/examples/agents/mcp-shop) · **Part of:** [Cameleer MCP](../mcp.md) ## What people ask, and what happens | request | what happened | |---|---| | Olivia Brown wants to swap the rain jacket from order 1011 for a different size. | the client showed a form, "Which size should we send for JKT-RAIN on order 1011?"; the user picked L; exchange EX-1 was created | | Exchange the jacket on order 1011 for another size. *(the user closes the form)* | nothing was exchanged; Claude said the size question was cancelled and offered to start again | ## A recorded conversation **User:** Olivia Brown wants to swap the rain jacket from order 1011 for a different size. Claude called `get_order`, then `exchange_item` with `{"orderId": 1011, "sku": "JKT-RAIN"}`. The route asked: > Which size should we send for JKT-RAIN on order 1011? with a choice of XS to XXL. The user chose L, the route finished, and Claude answered: > Olivia Brown's rain jacket exchange is set up. The reference is EX-1, for order 1011. > New size: L, which is the size you chose when asked. [...] The size L jacket will ship once > her original is scanned at the post office. The model never guessed the size: the answer came from the user, through the tool. ## How it is built The route sets the form's JSON Schema in `CamelAiToolElicitSchema`, puts the question in the body and sends it to `ai-tool:current?operation=elicit`. The answer comes back as the body and `CamelAiToolElicitAction` says whether the user accepted, declined or cancelled: ```yaml - route: id: exchange-item from: uri: ai-tool:exchange_item parameters: title: Exchange an item description: >- Exchange one item of a delivered order for another size, within 30 days of delivery. The tool asks the user which size to send; the customer returns the original with a prepaid label. tags: acme parameter.orderId: integer parameter.orderId.description: The order number parameter.orderId.required: true parameter.sku: string parameter.sku.description: The SKU of the item to exchange (get_order lists them) parameter.sku.required: true steps: - to: direct:load-order - to: "sql:select count(*) from order_lines where order_id = :#orderId and sku = :#sku?dataSource=jdbc:rustsql:mem:acme&outputType=SelectOne" - setHeader: name: hasLine simple: "${body}" - choice: when: - simple: "${header.order} == null" steps: - setHeader: name: CamelAiToolIsError constant: true - setBody: simple: "Order ${header.orderId} does not exist." - simple: "${header.orderStatus} != 'delivered'" steps: - setHeader: name: CamelAiToolIsError constant: true - setBody: simple: "Order ${header.orderId} is ${header.orderStatus}; only delivered items can be exchanged." - simple: "${header.hasLine} == 0" steps: - setHeader: name: CamelAiToolIsError constant: true - setBody: simple: "Order ${header.orderId} has no item ${header.sku}; get_order lists its SKUs." otherwise: steps: - setHeader: name: CamelAiToolElicitSchema constant: '{"type": "object", "properties": {"size": {"type": "string", "title": "New size", "enum": ["XS", "S", "M", "L", "XL", "XXL"]}}, "required": ["size"]}' - setBody: simple: "Which size should we send for ${header.sku} on order ${header.orderId}?" - to: ai-tool:current?operation=elicit - choice: when: - simple: "${header.CamelAiToolElicitAction} != 'accept'" steps: - setBody: simple: '{"orderId": ${header.orderId}, "status": "not exchanged", "note": "The user did not choose a size (${header.CamelAiToolElicitAction}); nothing was changed."}' otherwise: steps: - setHeader: name: size simple: "${body[size]}" - to: "sql:insert into exchanges (order_id, sku, size, created) values (:#orderId, :#sku, :#size, '{{acme.today}}') returning id?dataSource=jdbc:rustsql:mem:acme&outputType=SelectOne" - setBody: simple: '{"exchange": "EX-${body}", "orderId": ${header.orderId}, "sku": "${header.sku}", "newSize": "${header.size}", "note": "The tool asked the user which size to send, and the user chose ${header.size}.", "status": "replacement ships when the original is scanned at the post office; prepaid return label emailed"}' ``` - **The question is part of the tool,** so every client asks it the same way, and the model cannot skip it. - **Every outcome is handled.** Accept continues; decline or cancel returns "not exchanged ... nothing was changed". - **The result names who decided.** "The tool asked the user which size to send, and the user chose L" stopped smaller models from presenting the size as their own choice. - **Both eras work.** In 2026-07-28 the call returns `input_required` and the client retries with the answer; in a 2025-11-25 session or over stdio the server sends `elicitation/create` during the call. A client without the `elicitation` capability gets an error result, and nothing runs. A route can also send progress, log messages and sampling requests (ask the client's model) the same way; see [MCP server](../mcp-server.md#progress-logs-elicitation-and-sampling). ## Try it Run the shop, connect Claude Desktop (it shows elicitation forms) and ask for the exchange. `shop_use_cases` in `crates/cameleer-main/tests/mcp_shop.rs` answers the form with L, and cancels it in a second call, over MCP. ## Related - [A manager in the loop](manager-approval.md), [Actions guarded by approvals](approvals.md) - [Cameleer MCP](../mcp.md) ## Found a problem? If something on this page doesn't match what Cameleer does, please [open an issue](https://github.com/pmsudhi/cameleer/issues/new), or fork the repository, fix it, add a test, run `cargo test --workspace` and open a pull request.