feat: captain custom tools v1 (#13890)

# Pull Request Template

## Description

Adds custom tool support to v1

## Type of change
- [x] New feature (non-breaking change which adds functionality)


## How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide
instructions so we can reproduce. Please also list any relevant details
for your test configuration.

<img width="1816" height="958" alt="CleanShot 2026-03-24 at 11 37 33@2x"
src="https://github.com/user-attachments/assets/2777a953-8b65-4a2d-88ec-39f395b3fb47"
/>

<img width="378" height="488" alt="CleanShot 2026-03-24 at 11 38 18@2x"
src="https://github.com/user-attachments/assets/f6973c99-efd0-40e4-90fe-4472a2f63cea"
/>

<img width="1884" height="1452" alt="CleanShot 2026-03-24 at 11 38
32@2x"
src="https://github.com/user-attachments/assets/9fba4fc4-0c33-46da-888a-52ec6bad6130"
/>



## Checklist:

- [x] My code follows the style guidelines of this project
- [ ] I have performed a self-review of my code
- [ ] I have commented on my code, particularly in hard-to-understand
areas
- [ ] I have made corresponding changes to the documentation
- [ ] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged and published in downstream
modules

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Co-authored-by: Shivam Mishra <scm.mymail@gmail.com>

enterprise/app/models/captain/custom_tool.rb

@@ -24,6 +24,10 @@
 #  index_captain_custom_tools_on_account_id_and_slug  (account_id,slug) UNIQUE
 #
 class Captain::CustomTool < ApplicationRecord
+  class LimitExceededError < StandardError; end
+
+  MAX_PER_ACCOUNT = 15
+
   include Concerns::Toolable
   include Concerns::SafeEndpointValidatable
 
@@ -31,6 +35,10 @@ class Captain::CustomTool < ApplicationRecord
 
   NAME_PREFIX = 'custom'.freeze
   NAME_SEPARATOR = '_'.freeze
+  # OpenAI enforces a 64-char limit on function names. The slug is used
+  # verbatim as the tool name in LLM requests, so it must fit within this limit.
+  MAX_SLUG_LENGTH = 64
+  COLLISION_SUFFIX_LENGTH = 7 # "_" + 6 random alphanumeric chars
   PARAM_SCHEMA_VALIDATION = {
     'type': 'array',
     'items': {
@@ -52,8 +60,9 @@ class Captain::CustomTool < ApplicationRecord
   enum :auth_type, %w[none bearer basic api_key].index_by(&:itself), default: :none, validate: true, prefix: :auth
 
   before_validation :generate_slug
+  before_create :ensure_within_limit
 
-  validates :slug, presence: true, uniqueness: { scope: :account_id }
+  validates :slug, presence: true, uniqueness: { scope: :account_id }, length: { maximum: MAX_SLUG_LENGTH }
   validates :title, presence: true
   validates :endpoint_url, presence: true
   validates_with JsonSchemaValidator,
@@ -73,21 +82,29 @@ class Captain::CustomTool < ApplicationRecord
 
   private
 
+  def ensure_within_limit
+    # Lock the account row to serialize concurrent creates and prevent exceeding the cap
+    Account.lock.find(account_id)
+    return if account.captain_custom_tools.count < MAX_PER_ACCOUNT
+
+    raise LimitExceededError, I18n.t('captain.custom_tool.limit_exceeded', limit: MAX_PER_ACCOUNT)
+  end
+
   def generate_slug
     return if slug.present?
     return if title.blank?
 
-    paramterized_title = title.parameterize(separator: NAME_SEPARATOR)
-
-    base_slug = "#{NAME_PREFIX}#{NAME_SEPARATOR}#{paramterized_title}"
+    parameterized_title = title.parameterize(separator: NAME_SEPARATOR)
+    base_slug = "#{NAME_PREFIX}#{NAME_SEPARATOR}#{parameterized_title}".truncate(MAX_SLUG_LENGTH, omission: '')
     self.slug = find_unique_slug(base_slug)
   end
 
   def find_unique_slug(base_slug)
     return base_slug unless slug_exists?(base_slug)
 
+    truncated = base_slug.truncate(MAX_SLUG_LENGTH - COLLISION_SUFFIX_LENGTH, omission: '')
     5.times do
-      slug_candidate = "#{base_slug}#{NAME_SEPARATOR}#{SecureRandom.alphanumeric(6).downcase}"
+      slug_candidate = "#{truncated}#{NAME_SEPARATOR}#{SecureRandom.alphanumeric(6).downcase}"
       return slug_candidate unless slug_exists?(slug_candidate)
     end