Declarative Agent Developer

M365 Agent Developer

Telemetry Tagging

Before running any atk CLI commands, set the session environment variable so all CLI invocations are tagged as skill-initiated:

export ATK_CLI_SKILL=true

Run this once at the start of the session. All subsequent atk commands in the same terminal will inherit it.

⛔ Workspace Check — MANDATORY FIRST STEP

Before doing ANYTHING, check the workspace files to fingerprint the project:

1. Run npx -y --package @microsoft/m365agentstoolkit-cli atk --version to confirm ATK CLI is installed. If not found → Stop. Tell the user to install ATK.
2. Check for m365agents.yml or teamsApp.yml at the project root.
3. Check for appPackage/declarativeAgent.json.
4. Check for non-agent indicators (package.json with express/react/next, src/index.js, app.py, etc.)

Then follow the decision gate:

Detailed gate rules, examples, and anti-patterns: Workspace Gates

🚫 HARD REJECTION RULES — No Exceptions

These rules override ALL other instructions. If any of these apply, you MUST stop immediately.

1. NEVER create declarativeAgent.json yourself. If the manifest is missing and the user asked to edit/modify/deploy, respond with text only: explain the manifest is missing, suggest npx -y --package @microsoft/m365agentstoolkit-cli atk new or starting from scratch. Do NOT create the file, do NOT create appPackage/, do NOT "help" by scaffolding implicitly.

2. NEVER create files in a non-agent project. If the workspace is an Express/React/Django/etc. app without appPackage/, your response must be text-only. Do NOT create any files, do NOT run any commands.

3. NEVER deploy when errors exist. If the agent manifest has errors, STOP. Do NOT run npx -y --package @microsoft/m365agentstoolkit-cli atk provision — not "to test", not "to demonstrate the error", not "to see what happens". Report the errors and ask the user how to proceed.

🔍 Detect → Inform → Ask (Error-Handling Protocol)

When you encounter ANY problem (missing files, malformed JSON, validation errors, incompatible features), you MUST follow this sequence in order:

1. Detect — Identify the specific problem. For JSON issues, attempt to parse the file and report syntax errors. For missing fields, check the manifest against the Schema.
2. Inform — Tell the user BEFORE taking any action. Describe exactly what is wrong ("declarativeAgent.json has malformed JSON: missing comma on line 12, unclosed array on line 18").
3. Ask — Wait for the user's response before making changes. Do NOT silently fix, auto-correct, or work around the problem.

This protocol applies to:

• Missing declarativeAgent.json → Detect (file not found) → Inform ("no manifest found") → Ask ("would you like to create a new agent?")
• Malformed JSON → Detect (parse errors) → Inform (list specific syntax issues) → Ask ("should I fix these syntax errors?")
• Validation errors → Detect (parse and check manifest) → Inform (list all errors) → Ask ("how would you like to fix these?")
• Version incompatibility → Detect (feature requires newer version) → Inform ("this feature requires v1.6, your agent is v1.4") → Ask ("should I upgrade?")

Phase Routing

ATK CLI Setup

Before running any ATK commands, check if the ATK CLI is available by running npx -y --package @microsoft/m365agentstoolkit-cli atk --version. If not found, STOP and tell the user — do NOT attempt to install it yourself.

All commands use the npx -y --package @microsoft/m365agentstoolkit-cli atk prefix (e.g., npx -y --package @microsoft/m365agentstoolkit-cli atk provision --env local).

Critical Rules

1. Deploy After EVERY Edit

After ANY change to files in appPackage/, you MUST deploy and show the test link before responding:

npx -y --package @microsoft/m365agentstoolkit-cli atk provision --env local --interactive false

Then read M365_TITLE_ID from env/.env.local and ALWAYS present the review UX:

✅ Agent deployed successfully!

🚀 Test Your Agent in M365 Copilot:
🔗 https://m365.cloud.microsoft/chat/?titleId={M365_TITLE_ID}

⛔ Never respond without this link. If you deployed, the test link MUST appear in your response. This is not optional — it is how the user tests their agent.

• If the manifest has errors → STOP. Fix errors. Do NOT deploy.
• Exception: user explicitly asks you not to deploy

2. Never Invent Content or Create Missing Files

• Do NOT invent placeholder names, descriptions, or instructions
• Do NOT create declarativeAgent.json or appPackage/ if they don't exist — this is a REJECT scenario, not a "help by creating" scenario
• If required fields are missing, report the gaps, and ASK the user
• If JSON is malformed, follow Detect → Inform → Ask: parse the file first, tell the user what's broken, then ask before fixing. Use surgical edits (not rewrites)
• ⛔ NEVER set placeholder values for environment variables that are populated by automation (e.g., <PREFIX>_MCP_AUTH_ID, TEAMS_APP_ID). Leave them empty (VAR_NAME=). Placeholders will be treated as real values and will NOT be overwritten by provisioning.

3. Schema Version Compatibility

Before adding ANY feature, read the version field in declarativeAgent.json and check the Schema feature matrix. If the feature isn't supported in that version, refuse and offer to upgrade.

Key version gates:

• sensitivity_label, worker_agents, EmbeddedKnowledge → v1.6 only
• Meetings → v1.5+
• ScenarioModels, behavior_overrides, disclaimer → v1.4+
• Dataverse, TeamsMessages, Email, People → v1.3+

4. Use npx -y --package @microsoft/m365agentstoolkit-cli atk add action for API Plugins — NEVER Create Plugin Files Manually

You are forbidden from manually creating ai-plugin.json, OpenAPI specs, adaptive cards, or editing the actions array. Use the CLI:

# ⛔ Always list ALL operations in a single call — NEVER run separate calls per operation
npx -y --package @microsoft/m365agentstoolkit-cli atk add action --api-plugin-type api-spec --openapi-spec-location URL --api-operation "GET /path,POST /path,PATCH /path/{id},DELETE /path/{id}" -i false

Run a single npx -y --package @microsoft/m365agentstoolkit-cli atk add action call per OpenAPI spec, listing all operations as a comma-separated list in --api-operation. Never run separate npx -y --package @microsoft/m365agentstoolkit-cli atk add action calls for different operations from the same spec — this creates multiple plugins instead of one. If npx -y --package @microsoft/m365agentstoolkit-cli atk add action fails, report the error; do NOT fall back to manual creation.

Exception: MCP servers are not supported by npx -y --package @microsoft/m365agentstoolkit-cli atk add action. Use the MCP Plugin workflow instead.

5. MCP Server Integration

When the user mentions an MCP server URL, follow the MCP Plugin workflow. You MUST discover tools via the MCP protocol handshake (initialize → notifications/initialized → tools/list) — NEVER fabricate tool names/descriptions. For authenticated MCP servers, follow the authentication guide to configure OAuth.

6. Always Update Instructions & Starters After Changes

Adding a capability or plugin without updating instructions is incomplete. After ANY change:

1. Update instructions to describe the new/changed functionality — every data source should have clear intent coverage (WHEN and WHY to use it) per the Instruction Review quality bar. Built-in capabilities don't need exact names; actions/plugins should be named.
2. Do NOT list tool names, descriptions, or parameters in instructions — these are already in the plugin metadata (ai-plugin.json, MCP manifests, capability config). Instructions should contain decision logic only: WHEN to use each tool, chaining rules, and failure handling.
3. Stay within the 8,000-character instruction limit — if close to the limit, cut tool descriptions first
4. Add at least 1 conversation starter per added capability/plugin
5. Remove starters that reference removed capabilities
6. Run the Diagnostic Checklist against the updated instructions to verify quality

7. App Name Requirement

Always update the app name and description to something meaningful. Never leave defaults like "My Agent".

References

Shared

• Authentication — OAuth discovery, credentials, oauth/register lifecycle, OAuthPluginVault
• Best Practices — Security, performance, testing, compliance
• Conversation Design — Authoring instructions and conversation starters from scratch
• Instruction Review — Auditing, diagnosing, and improving existing instructions; anti-pattern detection; before/after rewrites
• Deployment — ATK CLI workflows, environments, CI/CD
• Localization — Multi-language support, tokenized manifests, language files
• Workspace Gates — Detailed gate rules, examples, anti-patterns

Scaffolding

• Scaffolding Workflow — Step-by-step scaffolding instructions, naming rules, error handling

JSON Development

• Editing Workflow — Step-by-step JSON development instructions
• Schema — Official JSON schema for agent manifests
• API Plugins — OpenAPI integration for JSON agents
• MCP Plugin — MCP server integration with RemoteMCPServer, OAuth, response semantics, logo handling
• Examples — JSON manifest examples

Source: microsoft/skills → .github/plugins/microsoft-365-agents-toolkit/skills/declarative-agent-developer/SKILL.md