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Elicitation enables MCP tools to request additional information from users during execution. This creates interactive workflows where tools can dynamically gather data, credentials, or approvals as needed.

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Understanding Elicitation

When a tool needs user input, it sends an elicitation request to the client. The client handles presenting this request to the user and returning their response. This enables:
  • Interactive workflows: Tools can ask for input mid-execution
  • Secure credentials: Request sensitive data without storing it
  • Dynamic decisions: Get user approval for actions
  • OAuth flows: Redirect users for authentication
Two Modes Available: Form mode for structured data collection, and URL mode for directing users to external authentication or approval pages.

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Elicitation Modes

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Form Mode

Collect structured data with JSON schema validation. Best for:
  • Non-sensitive information
  • Structured input requirements
  • Client-side form rendering

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URL Mode

Direct users to external URLs. Required for:
  • Sensitive credentials (passwords, API keys)
  • OAuth authentication flows
  • External approval processes
  • Third-party integrations
Server API: Servers use a simplified API like ctx.elicit(message, zodSchema) or ctx.elicit(message, url). The mode is automatically detected and the request is sent to the client with the appropriate JSON schema or URL.Server-Side Validation with mcp-use: When using the mcp-use server library with Zod schemas (simplified API), returned data is automatically validated server-side before reaching your tool logic. This is a convenience feature provided by mcp-use, ensuring type safety and data integrity.

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Configuration

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With MCPClient

Provide an onElicitation function when initializing the MCPClient. The elicitationCallback name is still supported but deprecated; use onElicitation. 
import { MCPClient } from "mcp-use";
import type {
  ElicitRequestFormParams,
  ElicitRequestURLParams,
  ElicitResult,
} from "@modelcontextprotocol/sdk/types.js";

async function onElicitation(
  params: ElicitRequestFormParams | ElicitRequestURLParams
): Promise<ElicitResult> {
  if (params.mode === "url") {
    // URL mode: Direct user to external URL
    console.log(`Please visit: ${params.url}`);
    console.log(`Reason: ${params.message}`);

    // Show URL to user (open in browser, display in UI, etc.)
    // In a real app, you might open a popup or new tab

    // Wait for user confirmation
    const userConsent = await promptUser("Did you complete the authorization?");

    return {
      action: userConsent ? "accept" : "decline",
    };
  } else {
    // Form mode: Collect structured data
    console.log(`Server requests: ${params.message}`);

    const schema = params.requestedSchema;
    const userData: Record<string, any> = {};

    // Collect data based on schema properties
    if (schema.type === "object" && schema.properties) {
      for (const [fieldName, fieldSchema] of Object.entries(
        schema.properties
      )) {
        const value = await promptUser(
          `Enter ${fieldSchema.title || fieldName}:`,
          fieldSchema.default
        );
        userData[fieldName] = value;
      }
    }

    return {
      action: "accept",
      content: userData,
    };
  }
}

const client = new MCPClient(config, { onElicitation });

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With React Hook

Use the onElicitation prop in the useMcp hook: 
import { useMcp } from "mcp-use/react";
import type {
  ElicitRequestFormParams,
  ElicitRequestURLParams,
  ElicitResult,
} from "@modelcontextprotocol/sdk/types.js";

function MyComponent() {
  const { tools, callTool, state } = useMcp({
    url: "http://localhost:3000/mcp",
    onElicitation: async (params) => {
      if (params.mode === "url") {
        // URL mode: Open external URL
        const confirmed = window.confirm(
          `${params.message}\n\nOpen ${params.url}?`
        );

        if (confirmed) {
          window.open(params.url, "_blank");

          // Wait for user to complete external action
          const completed = window.confirm("Did you complete the action?");
          return {
            action: completed ? "accept" : "decline",
          };
        }

        return { action: "decline" };
      } else {
        // Form mode: Show form to collect data
        const formData = await showElicitationForm(
          params.message,
          params.requestedSchema
        );

        return {
          action: formData ? "accept" : "cancel",
          content: formData ?? undefined,
        };
      }
    },
  });

  // ... rest of component
}

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Client helpers

mcp-use provides helpers so you don’t have to hand-roll defaults, validation, or result building. Import them (and types) from mcp-use or mcp-use/client. For a typed callback without importing the SDK, use OnElicitationCallback from mcp-use.
  • Defaults: getDefaults(params) — default values from the request schema; applyDefaults(params, partial?) — merge partial content with defaults; acceptWithDefaults(params) — return an accept result using schema defaults.
  • Result builders: accept(content), decline(reason?), cancel(), reject(reason?) (reject is an alias for decline).
  • Validation: validate(params, content) returns { valid: boolean; errors?: string[] } (Zod-based; uses requestedSchema). Types: ElicitContent, ElicitValidationResult.
Minimal form-mode example using acceptWithDefaults: 
import {
  acceptWithDefaults,
  type OnElicitationCallback,
  MCPClient,
} from "mcp-use";

const onElicitation: OnElicitationCallback = async (params) => {
  return acceptWithDefaults(params);
};

const client = new MCPClient(config, { onElicitation });
Optional: validate user input before accepting: 
import {
  accept,
  decline,
  validate,
  type OnElicitationCallback,
  MCPClient,
} from "mcp-use";

const onElicitation: OnElicitationCallback = async (params) => {
  const formData = await collectFormFromUser(params);
  const { valid, errors } = validate(params, formData);
  if (!valid) {
    await showErrors(errors);
    return decline(errors?.join("; "));
  }
  return accept(formData);
};

const client = new MCPClient(config, { onElicitation });

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Form Mode Elicitation

Form mode collects structured data from users with JSON schema validation.
Validation Flow: The client receives a JSON Schema to guide user input. When data is returned, the server validates it against the original Zod schema (if using simplified API) or JSON Schema (if using verbose API). This provides defense-in-depth validation.

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Request Parameters

FieldTypeDescription
mode"form" (optional)Specifies form mode (can be omitted for backwards compatibility)
messagestringHuman-readable prompt explaining what information is needed
requestedSchemaobjectJSON Schema defining the expected response structure

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Client-Side vs Server-Side Validation

Client-Side (Optional):
  • You can validate data before sending to improve UX
  • Shows errors immediately without round-trip
  • Not required - server validates anyway
Server-Side (Automatic):
  • Server always validates returned data
  • Ensures data integrity regardless of client behavior
  • Protects against malicious or buggy clients
  • Returns clear validation error messages
While the server always validates data, implementing client-side validation improves UX by catching errors before the round-trip. You can use the built-in validate(params, content) helper from mcp-use (Zod-based); no need to implement validateAgainstSchema yourself unless you need custom logic. 
import { validate, accept, cancel } from "mcp-use";

// After collecting formData from the user:
const { valid, errors } = validate(params, formData);
if (!valid) {
  await showErrorsToUser(errors ?? []);
  return cancel();
}
return accept(formData);
Best Practice: Implement client-side validation for better UX, but remember that the server always validates as the final authority. Never rely solely on client-side validation.

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Handling SEP-1330 Enum Schema Variants

For form-mode elicitation, clients should support these enum schema shapes:
VariantSchema ShapeRecommended UI
Untitled single-selecttype: "string" + enumSingle-select dropdown
Titled single-selecttype: "string" + oneOf[{ const, title }]Single-select dropdown with labels from title
Legacy titled enumtype: "string" + enum + enumNamesSingle-select dropdown using enumNames as labels
Untitled multi-selecttype: "array" + items.enumMulti-select checkbox group
Titled multi-selecttype: "array" + items.anyOf[{ const, title }]Multi-select checkbox group with labels from title
When returning accepted form values:
  • Single-select fields should return a string.
  • Multi-select fields should return an array of strings.
  • Use the const/enum values as submitted data, even when displaying a different label.
function getChoices(field: Record<string, any>): Array<{ value: string; label: string }> {
  if (Array.isArray(field.oneOf)) {
    return field.oneOf
      .filter((x) => typeof x?.const === "string")
      .map((x) => ({ value: x.const, label: x.title ?? x.const }));
  }

  if (Array.isArray(field.enum)) {
    return field.enum.map((value: string, i: number) => ({
      value,
      label: field.enumNames?.[i] ?? value,
    }));
  }

  return [];
}

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URL Mode Elicitation

URL mode directs users to external URLs for sensitive operations. This mode MUST be used for:
  • Authentication credentials
  • API keys and tokens
  • OAuth authorization flows
  • Payment information
  • Any sensitive personal data
Security Requirement: Never use form mode for sensitive data. URL mode ensures credentials and sensitive information do not pass through the MCP client, maintaining proper security boundaries.

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Request Parameters

FieldTypeDescription
mode"url"Specifies URL mode (required)
messagestringHuman-readable explanation of why the user needs to visit the URL
urlstringThe URL to direct the user to
elicitationIdstringUnique identifier for tracking this elicitation (auto-generated by server)

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Example: OAuth Authorization

async function handleUrlElicitation(
  params: ElicitRequestURLParams
): Promise<ElicitResult> {
  // Display the URL to the user
  const userMessage = `
    ${params.message}
    
    Please visit this URL to continue:
    ${params.url}
  `;

  console.log(userMessage);

  // In a browser environment, open in new tab
  if (typeof window !== "undefined") {
    window.open(params.url, "_blank", "noopener,noreferrer");
  }

  // Wait for user confirmation
  const completed = await confirmWithUser(
    "Have you completed the authorization?"
  );

  if (completed) {
    return { action: "accept" };
  } else {
    return { action: "decline" };
  }
}

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Response Structure

The elicitation callback must return an ElicitResult object: 
interface ElicitResult {
  action: "accept" | "decline" | "cancel";
  content?: ElicitContent; // Only for 'accept' action in form mode
}
ElicitContent is Record<string, string | number | boolean | string[]>.

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Response Actions

ActionWhen to UseField
acceptUser provided valid inputcontent required for form mode when accepting
declineUser explicitly declined to provide informationOmit
cancelUser dismissed the request without making a choiceOmit

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Error Handling

If no onElicitation handler is provided but a tool requests user input, the tool call will fail: 
// Without onElicitation handler
const client = new MCPClient(config);
// No onElicitation provided

// Tool that requires elicitation will fail
const session = await client.createSession("server-name");
try {
  await session.callTool("collect-user-info", {});
} catch (error) {
  console.error("Elicitation not supported:", error);
  // MCP error: Client does not support elicitation
}

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Next Steps