Build Your First AI Agent With Google Gemini Gems

You've probably used ChatGPT or Gemini to draft an email or answer a question. But every time you start a new conversation, you're starting from scratch — re-explaining who you are, what you need, and how you want the output formatted. Google Gemini Gems solve this by letting you build a reusable AI agent with saved instructions, personality, and context. No coding. No technical setup. This guide walks through building one from start to finish.

What a Gem Actually Is

A Gem is a custom version of Google Gemini that follows a specific set of instructions every time you use it. Think of it as a saved prompt — with a name, personality, and rules — that you can open anytime and start chatting with immediately.

Normal Gemini usage works like this: you open a new chat, explain what you need, provide context, specify the format, and get a response. If you want the same kind of output next week, you repeat all of that. A Gem skips the repetition. You define the instructions once, save the Gem, and every future conversation with that Gem follows the same rules automatically.

This matters because the biggest productivity gap in AI isn't the model's capability — it's the time spent re-explaining context in every new conversation.

Quick Facts

Cost: Gems are available on the free Gemini plan. Gemini Advanced ($19.99/month) unlocks more capable models and higher usage limits, but is not required to create and use Gems.
Where: Create and edit Gems at gemini.google.com (web only). Use them on web and mobile.
Files: You can upload up to 10 files per Gem for reference context (PDFs, docs, spreadsheets).
Sharing: Gems can be shared with others, similar to Google Drive permissions.

The Use Case: A Weekly Report Writer

Almost every professional writes some version of a weekly status report. It goes to a manager, a client, a team, or a stakeholder. The format is usually the same every week. The content changes, but the structure doesn't. And it takes 20–45 minutes to write properly — time that most people would rather spend on actual work.

This is a perfect Gem use case because:

The task is repetitive — it happens every week
The format is consistent — same sections, same tone, same audience
The input is messy — rough notes, bullet points, half-thoughts
The output needs to be polished — clear, professional, structured

The Gem StellarLink Media will build here takes rough weekly notes — bullet points, fragments, raw numbers — and transforms them into a polished, structured report with an executive summary, achievements, blockers, metrics, and next steps. Every week. In about two minutes instead of thirty.

Step 1: Open the Gem Builder

Go to gemini.google.com in your browser. On the left sidebar, click Explore Gems, then click New Gem (or navigate directly to gemini.google.com/gems/create).

You'll see two fields:

Name — give your Gem a descriptive name
Instructions — the detailed instructions that define how the Gem behaves

On the right side, there's a preview panel where you can test the Gem before saving.

Set the name to: Weekly Report Writer

Step 2: Write the Instructions

This is the core of the Gem. The instructions define everything: what the Gem does, how it formats output, what tone it uses, and what rules it follows. Good instructions produce consistently good output. Vague instructions produce inconsistent results.

StellarLink Media uses a structure based on the RODES framework (Role, Objective, Details, Examples, Sense Check) — a proven approach for structuring Gem instructions clearly.

Here are the complete instructions for the Weekly Report Writer Gem. You can copy these directly:

# ROLE
You are a professional report writer. You take rough, unstructured weekly notes and transform them into a polished, well-organized weekly status report suitable for managers, clients, or stakeholders.
# OBJECTIVE
When the user provides their raw weekly notes (bullet points, fragments, rough data), produce a complete weekly status report following the exact structure defined below.
# REPORT STRUCTURE
Every report must include these sections in this order:
1. **Executive Summary** — 2-3 sentences capturing the most important takeaway from the week. Lead with the headline, not background.
2. **Key Achievements** — 3-5 bullet points of completed work or milestones. Use action verbs (completed, launched, delivered, resolved). Include specific numbers where available.
3. **In Progress** — 2-4 bullet points of ongoing work with current status and expected completion.
4. **Blockers & Risks** — Any issues that could delay progress. If none, write "No blockers this week."
5. **Key Metrics** (if applicable) — Present any numbers or KPIs the user provides in a clean, scannable format.
6. **Next Week's Priorities** — 3-5 bullet points of what's planned for the following week.
# TONE AND STYLE
- Professional but not stiff. Clear and direct.
- Write for a busy reader who will scan, not read word-by-word.
- No filler phrases ("I'm pleased to report...", "This week was productive...").
- Use concrete language. "Reduced load time by 40%" is better than "Improved performance significantly."
- Keep the total report under 400 words unless the user provides extensive notes.
# RULES
- Do not invent information. Only use what the user provides. If details are missing, note the gap rather than guessing.
- If the user's notes are ambiguous, ask a clarifying question before producing the report.
- If the user says "same format as last time," produce the report in the same structure without asking again.
- Always end by asking: "Anything you'd like me to adjust before finalizing?"
# SENSE CHECK
If the user's input is unclear or seems incomplete, ask for clarification before generating the report. Do not produce a report from insufficient information.

After pasting these instructions, you'll notice a magic wand icon at the bottom of the text box. Clicking it lets Gemini suggest improvements to your instructions. This is optional — the instructions above are ready to use as-is, but the magic wand can help you customize them further for your specific reporting style.

Step 3: Test It in the Preview Panel

Before saving, test the Gem using the preview panel on the right. Enter a realistic set of rough notes and see what the Gem produces.

Here's a sample input you can paste to test:

Sample input:

- shipped the new dashboard to prod on tuesday, finally

- 3 bugs from QA fixed, 1 still open (the export thing)

- met with design team about the mobile redesign, they need another week for mockups

- onboarded 2 new team members, took most of wednesday

- API response time down to 120ms from 340ms after the caching changes

- still waiting on legal for the data processing agreement, been 2 weeks now

- next week: start mobile redesign implementation, finish the export bug, prep for quarterly review

The Gem should transform these rough notes into a structured report with all six sections. Check for:

Does it follow the section structure?
Did it avoid inventing details that weren't in the notes?
Is the tone professional but direct?
Is the executive summary actually a summary, not a list?
Did it ask if adjustments are needed at the end?

If anything is off, adjust the instructions and test again. This iterative loop — adjust, test, adjust — is how you build a Gem that works reliably.

Step 4: Save and Start Using It

Once you're satisfied with the preview output, click Save. The Gem now appears in your Gem library on the left sidebar.

Every Friday (or whenever you write your report), the workflow becomes:

Open the Weekly Report Writer Gem
Paste or type your rough notes for the week
Review the generated report
Ask the Gem to adjust anything ("make the executive summary shorter" or "move the API metric to the top")
Copy the final version into your email, Slack, or document

The entire process takes 2–5 minutes instead of 20–45.

Step 5: Refine Over Time

A Gem is not a set-and-forget tool. The best Gems get refined over the first few uses as you notice patterns in the output that need adjustment.

After using the Weekly Report Writer for 2–3 weeks, you'll likely notice things like:

The executive summary is too long or too short for your audience
The tone is slightly too formal (or too casual) for your team culture
You want a specific section your company uses (like "Client Updates" or "Budget Status")
Certain types of notes consistently get misinterpreted

To fix these, go back to the Gem manager, click into your Gem, and update the instructions. Each fix makes the Gem more useful for your specific context. After 3–4 rounds of refinement, the Gem will produce output that needs almost no editing.

A practical refinement loop:

Use the Gem for your actual weekly report
Note what you had to manually fix in the output
Add a specific instruction to prevent that issue (e.g., "Never start bullet points with 'Successfully' — lead with the action verb directly")
Test the updated Gem with the same input to confirm the fix works

Going Further: File Uploads

Gems support uploading up to 10 files as reference material. This opens up more sophisticated use cases:

Upload a sample report — give the Gem an example of a report your manager or client loves, and add an instruction like "Match the structure and tone of the uploaded sample report." The Gem will mimic that specific style.
Upload a brand style guide — if your organization has specific language rules (e.g., "always write 'customers' not 'users'"), upload the guide and instruct the Gem to follow it.
Upload a project brief — give the Gem context about the project so it understands terminology and priorities without you re-explaining them every week.

File uploads turn a simple Gem into something closer to a context-aware assistant that understands your specific work environment.

Five More Gems Worth Building

The Weekly Report Writer demonstrates the pattern. Here are five more Gems that follow the same logic — repetitive task, consistent format, messy input, polished output:

Meeting Notes to Action Items — Paste raw meeting notes or a transcript. The Gem extracts decisions made, action items with owners, and open questions. Include instructions for formatting action items as "WHO will do WHAT by WHEN."
Client Email Drafter — Define your communication style, level of formality, and common phrases. Provide the situation in a few bullet points, and the Gem drafts a complete client email. Upload your email signature format as a reference file.
Proposal Section Writer — Upload your proposal template. The Gem takes a project description and generates specific sections (scope, timeline, pricing rationale) in your company's standard format.
Social Post Generator — Define your LinkedIn voice, post structure (hook, body, CTA), and topics. Give it a rough idea or article link, and it produces a ready-to-post draft.
Interview Prep Coach — Upload a job description and your resume. The Gem generates likely interview questions, suggests answers based on your experience, and identifies gaps to prepare for.

Each of these follows the same build process: identify the task, define the structure, write clear instructions, test, refine.

The Takeaway

Gemini Gems are the simplest way to go from "using AI occasionally" to "using AI as a reliable part of your workflow." The difference is not the model's capability — it's the elimination of repetitive context-setting that makes one-off AI usage feel slow and inconsistent.

The playbook is straightforward:

Find a repetitive task with a consistent format
Write clear instructions using the RODES structure (Role, Objective, Details, Examples, Sense Check)
Test with real inputs, not hypothetical ones
Refine the instructions over 2–3 uses based on what you actually had to fix
Upload reference files to give the Gem deeper context about your specific environment

A well-built Gem doesn't just save time on one task. It changes the economics of how you work with AI — from a tool you use when you remember to, to an assistant that's ready every time you need it.

Sources

Google — Gemini Gems: Build Custom AI Experts
Google Support — Get Started With Gems in Gemini Apps
Google Support — Tips for Creating Custom Gems
Google Blog — How to Use Gems, Google's Custom AI Tools
TechCrunch — Google Now Lets You Share Custom Gemini AI Assistants Known as Gems (September 2025)
Leon Nicholls / Medium — The Ultimate Guide to Google Gemini Gems (RODES Framework)
9to5Google — What Gemini Features You Get With Google AI Plus, Pro, & Ultra (February 2026)