feat(mcp): accept field-fill params on send_documents tool

Mirror the REST API by accepting values, fields, readonly_fields,
metadata, external_id, completed, role and message per submitter.
Input is normalized via Submissions::NormalizeParamUtils so field
names resolve to UUIDs and default_value entries merge into values.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

lib/mcp/tools/send_documents.rb

@@ -3,6 +3,11 @@
 module Mcp
   module Tools
     module SendDocuments
+      SUBMITTER_KEYS = %w[
+        email name phone role completed external_id
+        metadata values readonly_fields message fields
+      ].freeze
+
       SCHEMA = {
         name: 'send_documents',
         title: 'Send Documents',
@@ -31,6 +36,60 @@ module Mcp
                   phone: {
                     type: 'string',
                     description: 'Submitter phone number in E.164 format'
+                  },
+                  role: {
+                    type: 'string',
+                    description: 'Template role name (required when the template has multiple roles)'
+                  },
+                  completed: {
+                    type: 'boolean',
+                    description: 'Mark this submitter as already completed (skips the signing UI)'
+                  },
+                  external_id: {
+                    type: 'string',
+                    description: 'Your application identifier for this submitter'
+                  },
+                  metadata: {
+                    type: 'object',
+                    description: 'Arbitrary key/value metadata stored on the submitter',
+                    additionalProperties: true
+                  },
+                  values: {
+                    type: 'object',
+                    description: 'Pre-fill field values, keyed by field UUID or field name',
+                    additionalProperties: true
+                  },
+                  readonly_fields: {
+                    type: 'array',
+                    description: 'Field names to mark read-only for this submitter',
+                    items: { type: 'string' }
+                  },
+                  message: {
+                    type: 'object',
+                    description: 'Custom email subject/body sent to this submitter',
+                    properties: {
+                      subject: { type: 'string' },
+                      body: { type: 'string' }
+                    }
+                  },
+                  fields: {
+                    type: 'array',
+                    description: 'Per-field overrides (default_value, title, required, validation, etc.)',
+                    items: {
+                      type: 'object',
+                      properties: {
+                        name: { type: 'string', description: 'Field name as defined in the template' },
+                        uuid: { type: 'string', description: 'Field UUID (use instead of name to target a specific field)' },
+                        default_value: { description: 'Pre-filled value the submitter can still edit; string or array depending on field type' },
+                        value: { description: 'Locked value (cannot be edited); string or array depending on field type' },
+                        title: { type: 'string' },
+                        description: { type: 'string' },
+                        readonly: { type: 'boolean' },
+                        required: { type: 'boolean' },
+                        validation_pattern: { type: 'string' },
+                        invalid_message: { type: 'string' }
+                      }
+                    }
                   }
                 }
               }
@@ -48,7 +107,7 @@ module Mcp
 
       module_function
 
-      # rubocop:disable Metrics/MethodLength
+      # rubocop:disable Metrics/MethodLength, Metrics/AbcSize
       def call(arguments, current_user, current_ability)
         template = Template.accessible_by(current_ability).find_by(id: arguments['template_id'])
 
@@ -59,17 +118,19 @@ module Mcp
         return { content: [{ type: 'text', text: 'Template has no fields' }], isError: true } if template.fields.blank?
 
         submitters = (arguments['submitters'] || []).map do |s|
-          s.slice('email', 'name', 'role', 'phone')
+          s.slice(*SUBMITTER_KEYS).compact.with_indifferent_access
-           .compact_blank
-           .with_indifferent_access
         end
 
+        submissions_attrs = [{ submitters: submitters }.with_indifferent_access]
+
+        Submissions::NormalizeParamUtils.normalize_submissions_params!(submissions_attrs, template, purpose: :api)
+
         submissions = Submissions.create_from_submitters(
           template:,
           user: current_user,
           source: :api,
           submitters_order: 'random',
-          submissions_attrs: { submitters: submitters },
+          submissions_attrs:,
           params: { 'send_email' => true, 'submitters' => submitters }
         )
 
@@ -105,10 +166,11 @@ module Mcp
             }
           ]
         }
-      rescue Submissions::CreateFromSubmitters::BaseError => e
+      rescue Submitters::NormalizeValues::BaseError, Submissions::CreateFromSubmitters::BaseError,
+             DownloadUtils::UnableToDownload => e
         { content: [{ type: 'text', text: e.message }], isError: true }
       end
-      # rubocop:enable Metrics/MethodLength
+      # rubocop:enable Metrics/MethodLength, Metrics/AbcSize
     end
   end
 end