How to generate documents from templates with AI agents using MCP Leave feedback
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Run the GroupDocs.Assembly MCP server locally and your agent can turn a template plus a few facts into a finished document — it asks the template what data it needs, fills that in, and the engine renders the contract, invoice or letter. Nothing is uploaded:
dnx GroupDocs.Assembly.Mcp --yes
What data does contract-template.docx need? Fill it for Contoso Pharma with the three services below and save it as a PDF.
NoteThe commands and config snippets on this page are for the .NET build of the server — the only platform available today. Installation and client setup: MCP server for .NET. Other platforms will expose the same tools with their own launch command; everything else on this page applies unchanged.
- The .NET 10 SDK (or Docker) and the server registered in your AI client — quick start.
- A template with
<<…>>tags in the storage folder (GROUPDOCS_MCP_STORAGE_PATH). The one below has a header, a services table that repeats per item, a total and a conditional discount line:
Service Agreement <<[contract.Number]>>
Date: <<[contract.Date]:"d MMMM yyyy">>
Customer: <<[customer.Name]>>, <<[customer.Address]>>
| <<foreach [item in items]>><<[item.Title]>> | <<[item.Quantity]>> | ...
| <<[item.UnitPrice]>> | <<[item.Quantity * item.UnitPrice]>><</foreach>> |
Total: <<[items.Sum(i => i.Quantity * i.UnitPrice)]>> EUR
<<if [contract.Discount > 0]>>A discount of <<[contract.Discount]>> percent
applies.<</if>>
user agent Assembly MCP server
| "Make the contract for this order: Contoso Pharma, 12 months ..." |
|---------------->| |
| |-- get_template_fields ------------------------->|
| | {"template":{"filePath": |
| | "contract-template.docx"}} |
| |<- {"dataSourceNames":["contract","customer", |
| | "items"], "dataSkeleton":{"customer":{"Name": |
| | ""...}, "items":[{"Title":"","Quantity":0}]}} -|
| | the agent fills the skeleton from the order |
| |-- assemble_document --------------------------->|
| | {"template":{...},"dataJson":"{...}", |
| | "format":"pdf"} |
| |<- "Assembled 'contract-template.docx' with inline |
| | JSON (JSON object) as PDF" --------------------|
|<- "Contract SA-2026-118 is ready: 3 services, total 75500 EUR." |
the model writes the data; layout, tables and wording come from the template
- Ask the template —
get_template_fieldsreturns the data names and a JSON skeleton. - Fill the data — the agent writes the skeleton’s values from your message.
- Render —
assemble_documentfills the template and saves the document.
Captured from server 26.11.0 (the evaluation note that opens each response is trimmed):
-> get_template_fields {"template":{"filePath":"contract-template.docx"}}
<- { "tagCount": 17,
"dataSourceNames": [ "contract", "customer", "items" ],
"dataSkeleton": {
"contract": { "Number": "", "Date": "", "Discount": "" },
"customer": { "Name": "", "Address": "", "Contact": "", "Email": "" },
"items": [ { "Title": "", "Quantity": 0, "UnitPrice": 0 } ] } }
-> assemble_document {"template":{"filePath":"contract-template.docx"},
"dataJson":"<the filled skeleton>","format":"pdf"}
<- Assembled 'contract-template.docx' with inline JSON (JSON object) as PDF
Saved to: …/contract-template_assembled.pdf
The data the agent passed:
{"contract":{"Number":"SA-2026-118","Date":"2026-11-12T00:00:00",
"Discount":5},
"customer":{"Name":"Contoso Pharma","Address":"Keizersgracht 210, Amsterdam",
"Contact":"Dr. Lena Brandt",
"Email":"lena.brandt@contoso.example"},
"items":[{"Title":"Managed hosting","Quantity":12,"UnitPrice":4800},
{"Title":"24/7 support","Quantity":12,"UnitPrice":1200},
{"Title":"Onboarding workshop","Quantity":1,"UnitPrice":3500}]}
The server prints the full path inside your storage folder; it is shortened here.
contract-template_assembled.pdf: the services table has three rows (57600, 14400 and 3500 EUR), the total reads 75500 EUR, the discount line appears because Discount is 5, and the date reads 12 November 2026. In evaluation mode the first line of the document is “Evaluation Only. Created with GroupDocs.Assembly 26.7…”.
| Symptom | Cause | Fix |
|---|---|---|
| “Can not get the value of member ‘Email’ … The template reads ‘Email’, which the data does not have.” | a field missing from the data (names are case-sensitive) | add it, or allowMissingMembers: true |
{{name}} printed as is | not Assembly syntax | write <<[name]>> — get_template_fields flags it |
| A date one day early | a date-only ISO string on a machine east of UTC | "2026-11-12T00:00:00" and a format in the template |
Can the agent change the layout? Not through this server — and that is the point. Change the template in Word, Excel or PowerPoint; the next run uses it.
Which output formats? The template’s own, or any save format of its family — PDF for every family; HTML and Markdown for Word templates. See supported formats.
Do I need to write the JSON myself? No. The agent writes it from the skeleton; you check the values.
Agents follow project instructions about when to use a tool. Paste this into the instruction file your agent reads (CLAUDE.md, AGENTS.md, .github/copilot-instructions.md, .cursorrules):
To produce a contract, invoice or letter, never write the document yourself:
call get_template_fields on the template in ./templates, fill its dataSkeleton
from the user's facts, then assemble_document with dataJson. Show the data first.
- Evaluation mode: every generated document starts with an Evaluation Only line, workbooks gain a worksheet, and e-mail templates lose their HTML body. Licensing.
<<[name]>>, not{{name}}: other engines’ placeholders stay in the output as text.- Templates are trusted input: image and document tags load the paths and URLs their expressions return.
- Dates: write them as
"2026-11-12T00:00:00"and format them in the template; a date-only string can shift by a day on machines east of UTC.
- One document per record (mail merge)
- Reports with tables and charts
- Inspect and fix a template
- From notes or email to a document
- Reports from repository data
- On-premise deployment
- Tools reference · Licensing · Troubleshooting & FAQ
- Questions: Assembly forum
- Let the model fill in the data, not write the document — the same scenario on the GroupDocs blog, with worked examples and the trade-offs.
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