Connect
Optimize
Secure
Candidate Re-Engagement
Revive Your Silver Medalists
Use StackOne to connect your AI agent to your ATS and email tools to automate candidate re-engagement.
AI Agents
Connect
MCP and A2A to REST, SOAP, and proprietary APIs.
Optimize
Tool discovery, data shaping, and reliable execution.
Secure
Scoped permissions, audit trails, and observability.
StackOne Integration Layer
list_candidates
greenhouse 
get_candidate
greenhouse
get_job
greenhouse
send_email
gmail 
send_message
slack 
Ask your agent...
StackOne Integration LayerConnect
200+ connectors, build your own, and multi-protocol support.
Optimize
Context, token, and speed optimization infrastructure.
Secure
Permissions API and prompt injection protection.
What Can AI Agents Do for Candidate Re-Engagement?
Your agent watches for new openings, searches past finalists, ranks them by fit, and sends personalized outreach — all before a job ad goes live.
01
Detect New Requisitions
Listen for new or approved job requisitions in Greenhouse, Lever, or Workday and trigger the re-engagement workflow automatically.
02 
Search Silver-Medal Candidates
Query the ATS for past applicants who reached final interview stages on similar roles but were not hired. Pull skills, location, and interview performance data from Lever, iCIMS, or SmartRecruiters.
03
Filter, Rank, and Match
Exclude candidates in active processes or marked do-not-contact. Rank the rest by skills match, recency, and interview performance against the new role requirements.
04
05
Log Activity in the ATS
Record every outreach action against the candidate record, update their status to re-engaged, and link them to the new requisition in Greenhouse or Workday.
06
Monitor Responses
Flag interested candidates for recruiter follow-up. Notify the hiring team via Slack and generate a summary report with re-engagement rates.
01
Detect New Requisitions
Listen for new or approved job requisitions in Greenhouse, Lever, or Workday and trigger the re-engagement workflow automatically.
02
Search Silver-Medal Candidates
Query the ATS for past applicants who reached final interview stages on similar roles but were not hired. Pull skills, location, and interview performance data from Lever, iCIMS, or SmartRecruiters.
03
Filter, Rank, and Match
Exclude candidates in active processes or marked do-not-contact. Rank the rest by skills match, recency, and interview performance against the new role requirements.
05
Log Activity in the ATS
Record every outreach action against the candidate record, update their status to re-engaged, and link them to the new requisition in Greenhouse or Workday.
06
Monitor Responses
Flag interested candidates for recruiter follow-up. Notify the hiring team via Slack and generate a summary report with re-engagement rates.
Why Building a Good Candidate Re-Engagement Agent Is Hard
Connecting to Many ATS and Email Providers
The agent must reach Greenhouse, Lever, Workday, iCIMS, SmartRecruiters, plus email providers like Gmail and SendGrid. Building each connector — auth, pagination, rate limits — is a massive lift that compounds with every new customer.
Token Cost Grows with Candidate Volume
Without a search-first approach, the agent pre-loads every ATS and email action definition into its context window. At high outreach volume, that burns tokens on irrelevant tools before the agent even starts matching candidates.
No Reliable Event Triggers Across ATS Platforms
Firing re-engagement when a requisition opens requires real-time events. ATS providers have different webhook and polling mechanisms, making consistent triggering hard to build and maintain across providers.
Candidate Data Carries Prompt Injection Risk
Candidate records contain free-text fields — resumes, interview notes, rejection reasons — that flow into agent prompts as untrusted input. Without a guard, injected instructions could alter agent behavior or leak data from other candidates.
How StackOne Makes Candidate Re-Engagement Agents Possible
Everything your re-engagement agent needs to search past candidates, send outreach, and log activity — with the controls IT demands.
200+ connectors with 10K+ agent-optimized actions
Pre-built connectors for Greenhouse, Lever, Workday, iCIMS, SmartRecruiters, Gmail, and SendGrid with full native action coverage and agent instructions included.
Managed Auth handles credentials across providers
OAuth flows, API keys, and token refresh managed per tenant for every connected ATS and email provider — agents never touch raw credentials.
Search and execute finds the right action
Agent searches StackOne's action catalog by natural language and executes the matching ATS or email action — no pre-loading thousands of tool definitions.
Managed Webhooks deliver requisition events consistently
StackOne subscribes to requisition lifecycle events across connected ATS platforms, handling registration, retries, and delivery differences so the agent triggers at the right moment.
AI Connector Builder extends to any ATS
Build custom connectors for niche or homegrown ATS platforms via REST, SOAP, or GraphQL — onboard any customer without bespoke engineering.
Defender blocks prompt injection from candidate data
StackOne Defender screens inbound candidate text for injection attempts before the agent processes it, preventing adversarial content in resumes or notes from manipulating outreach behavior.
You Control What the Agent Can Do
Scoped permissions define exactly which candidate fields the agent reads and which outreach actions it can trigger. Full audit trail of every operation for GDPR and CCPA compliance.
Integrates with your entire recruiting stack. Whatever it is.
Connect Any Agent to Automate Candidate Re-Engagement
Any Agent Framework
Claude, OpenAI, LangChain, Vercel AI SDK, CrewAI, Pydantic AI — StackOne works with every major agent framework out of the box.
Any Agent Builder
Whether you're building with code, a visual builder, or an enterprise platform — StackOne provides the integration layer your agent needs.
Connect Your Agent to Your Recruiting Stack
Start building in minutes. MCP connectors to every system your agent needs.
Frequently Asked Questions
The hardest parts are connecting to every customer's ATS (Greenhouse, Lever, Workday each have different auth and pagination), keeping token costs down when the agent searches thousands of past candidates, and guarding against prompt injection from free-text resume and rejection-reason fields.
Each customer runs a different ATS with proprietary APIs, unique OAuth flows, and different rate limits. Your agent needs connectors for all of them — plus email providers for outreach. Building and maintaining each connector is a significant engineering lift that compounds with every new customer.
Each ATS exposes different endpoints, data models, and authentication methods — Greenhouse uses API keys, Lever uses OAuth, Workday uses SOAP. An integration layer that handles managed auth and per-provider API logic lets the agent query candidates across all systems without per-platform connector code.
Niche ATSs like Ashby, Bullhorn, or homegrown systems lack pre-built agent tooling. A connector builder that maps REST, SOAP, or GraphQL endpoints into agent-ready actions lets you onboard any customer's ATS without bespoke engineering for each one.
Pre-loading every ATS and email action definition into context burns tokens at scale. A search-first approach lets the agent query an action catalog by natural language and load only the relevant tool — cutting context size and cost per candidate search dramatically.
Firing re-engagement at the right moment requires knowing when a new requisition opens. ATS providers deliver events differently — some offer webhooks, others need polling. StackOne's managed webhooks normalize event delivery across providers so the agent triggers consistently without per-ATS event infrastructure.
Candidate records contain free-text fields — resumes, interview notes, rejection reasons — that enter agent prompts as untrusted input. Without a dedicated prompt injection guard, a crafted string in a resume could override agent instructions and alter outreach behavior or leak data from other candidates.
The agent must access only the candidate fields each customer has authorized — not the full ATS dataset. Scoped permissions per connector enforce field-level access, while request-level observability logs every read and write for audit trails required by GDPR and CCPA.
Other Recruiting Use-Cases
View all Job Posting Distribution
Use StackOne to connect your AI agent to your ATS and job boards to automate job posting distribution.
View → Reference Check Automation
Use StackOne to connect your AI agent to your ATS, survey tools, and messaging systems to automate reference checks.
View → Offer Letter Generation
Use StackOne to connect your AI agent to your ATS, HRIS, and document management tools to automate offer letter generation.
View → Candidate Sourcing
Use StackOne to connect your AI agent to your ATS, talent CRM, and outreach tools to automate candidate sourcing and outreach.
View → Application Screening
Use StackOne to connect your AI agent to your ATS, document stores, and messaging tools to automate application screening and shortlisting.
View →Connect Your Agent to Your Recruiting Stack
Start building in minutes. MCP connectors to every system your agent needs.