MCP resources are read-only files from Celigo file storage that you expose to AI agents through an MCP server. When an agent is connected to an MCP server with resources configured, it can list available files using resources/list and retrieve their content using resources/read, giving it stable, structured grounding data (such as configuration files, reference tables, schemas, or policy documents) without modifying external systems.
MCP resources and Celigo file storage are co-released. You must have files uploaded to file storage before you can attach them as resources.
Adding resources to an MCP server lets you:
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Ground agents in static reference data so they can make accurate, context-aware decisions without guessing.
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Reuse the same files across multiple MCP servers and agents without duplicating content.
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Keep grounding content separate from executable tools, ensuring agents can read information without side effects.
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Control which files agents can access by enabling or disabling individual resources without removing them from the server.
When you add resources to an MCP server:
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You select files from Celigo file storage and attach them to the MCP server as resources.
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Agents connected to the server via an MCP connection discover available resources through resources/list.
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At runtime, the agent retrieves a resource's content via resources/read. The content is returned as a read-only payload the agent uses to inform its decisions or populate prompts.
Resources are strictly read-only and static. They do not support dynamic URI templates and cannot trigger side effects or write to external systems.
Each resource file must be 3 MB or smaller. Files larger than 3 MB can be attached to the MCP server, but agents will receive an error when attempting to read them. To avoid this, check the file size in Celigo file storage before adding a resource.
Prerequisites:
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You must have an MCP server already created. See Create an MCP server for setup details.
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Files must already be uploaded to Celigo file storage. See Celigo file storage to get started.
To add a resource:
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While creating an MCP server, on the right side, in the Capabilities section click Add. The Add capabilities page is displayed.
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On the top of the page, click Resources. If you don’t have any existing resources click Add resources.
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If no resources have been added yet, the Resources tab displays: "No resources available. Add resources here or verify they are enabled on your MCP server to make them available for your agents."
If you have previously added a resource, click + Add resources on the upper right side of the page.
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The Add resources window opens, showing your Celigo file storage folders and files. Select the files you want to add.
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Check the box next to each file you want to add.
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Folders cannot be selected. Click a folder to open it and select files inside it.
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The parent folder shows how many files are selected inside it.
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Files must be under 3 MB to be read by agents. Larger files can be attached but return an error when an agent reads them.
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Click Save & close to apply your selection and return to the Add capabilities page.
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The Resources section lists your added files, showing the following details:
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The file title (from Celigo file storage)
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The file path (its location in file storage)
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Description
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Size
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To remove a resource, click the delete icon in the Actions column.
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Click Save.
The resources are now attached to the MCP server. Any agent connected to this server through an MCP connection can discover and read them.
After you add resources to an MCP server, they appear as Resource in the Capabilities section of the MCP server configuration page. For each resource you have options to:
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Enable/Disable: Disabled resources remain listed in the Capabilities section but are not accessible to agents at runtime.
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View: Click to view it in the flow builder and close it.
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Delete - Click to remove the resource from the MCP server.
Note
Removing a resource from an MCP server does not delete the underlying file from Celigo file storage. However, if you delete a file directly from Celigo file storage, it will no longer be listed or available in the MCP server.
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Configure: Click the gear icon to rename the resource and click Save.
Resources tab is empty after saving
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Confirm the files you selected are still present in Celigo file storage.
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Verify you clicked Save on the MCP server configuration page after completing the Add capabilities flow, changes are not persisted until the server is saved.
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Refresh the page and check the Capabilities section again.
Agent receives an error when reading a resource
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Check that the file is under 3 MB. Resources larger than 3 MB return an error on resources/read. Replace the file with a smaller version in Celigo file storage, then re-attach it.
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Check that the resource's enable/disable toggle is on in the Capabilities section.
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Confirm the MCP server itself is toggled On in the MCP servers list (AI studio → MCP servers).
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Verify the agent uses an MCP connection that points to the correct MCP server.
Agent cannot retrieve a resource
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Confirm the MCP server is toggled On in AI studio → MCP servers.
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Verify the agent's MCP connection points to the correct MCP server.
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Check that the resource toggle is enabled on the server's Capabilities section.
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Check if access tokens are active and properly allocated.
Agent sees outdated resource content
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Resources are served from Celigo file storage. If you update the source file, upload the new version to file storage and re-attach it to the MCP server, or wait for the cache to refresh, the server automatically retries, fetching fresh content when a cached download link expires.