AI Agent for 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.

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AI Agents

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MCP and A2A to REST, SOAP, and proprietary APIs.

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Tool discovery, data shaping, and reliable execution.

Secure

Scoped permissions, audit trails, and observability.

StackOne Integration Layer

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greenhouse

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StackOne Integration Layer

Connect

450+ connectors, build your own, and multi-protocol support.

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Optimize

Context, token, and speed optimization infrastructure.

Falcon execution engine →

Secure

Permissions API and prompt injection protection.

Agent governance and safety →

What Can AI Agents Do for Candidate Re-Engagement?

An AI agent for candidate re-engagement connects to your ATS apps through StackOne to watch for new openings, search past finalists, rank them by fit, and send personalized outreach 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

Send Personalized Outreach

Generate tailored re-engagement emails referencing the candidate's previous application and the new role's selling points. Send via Gmail or SendGrid.

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.

04

Send Personalized Outreach

Generate tailored re-engagement emails referencing the candidate's previous application and the new role's selling points. Send via Gmail or SendGrid.

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

Building a good candidate re-engagement agent is hard because it has to connect to many ATS and email providers, keep token costs down as candidate volume grows, work without reliable event triggers across ATS platforms, and defend against prompt injection in candidate data.

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

StackOne makes candidate re-engagement agents possible by connecting them to your ATS apps, so one agent can search past candidates, send outreach, and log activity with the controls IT demands.

450+ connectors with 28,000+ agent-optimized actions

Pre-built connectors for Greenhouse, Lever, Workday, iCIMS, SmartRecruiters, Gmail, and SendGrid with full native action coverage and agent instructions included.

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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.

Agent Auth →

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.

Tools Discovery →

Build agentic workflows

Subscribe your AI agents to any webhook-enabled ATS connector and trigger agentic workflows from any of your app events.

Webhooks for AI agents →

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.

Connector Builder →

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.

Prompt Injection Defense →

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.

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Integrates with your entire recruiting stack. Whatever it is.

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Automate Candidate Re-Engagement with any AI agent through StackOne

Any AI Agent Client or 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.

MCP REST API A2A

Any Protocol

Pick the protocol that fits your stack. Tool calling, direct API integration, agent-to-agent messaging, or structured action workflows — all supported out of the box.

Connect Your Agent to Your Recruiting Stack

Start building in minutes. MCP connectors to every system your agent needs.

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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

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Job Posting Distribution

Use StackOne to connect your AI agent to your ATS and job boards to automate job posting distribution.

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Reference Check Automation

Use StackOne to connect your AI agent to your ATS, survey tools, and messaging systems to automate reference checks.

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Offer Letter Generation

Use StackOne to connect your AI agent to your ATS, HRIS, and document management tools to automate offer letter generation.

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Candidate Sourcing

Use StackOne to connect your AI agent to your ATS, talent CRM, and outreach tools to automate candidate sourcing and outreach.

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Application Screening

Use StackOne to connect your AI agent to your ATS, document stores, and messaging tools to automate application screening and shortlisting.

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