Upload an expense attachment to Sanka from an already available base64 payload. Prefer this direct upload for ordinary receipt/invoice PDFs when the client can pass content_base64 reliably. For client-local PDFs or payloads that are too large or unreliable to pass as one content_base64 string, us...
AI agents use upload_expense_attachment to create or update resources in Sanka MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Sanka MCP Server environment.
This is a Write operation because it creates or stores new attachment data within the system. It is reversible (attachments can typically be deleted or replaced) and does not execute arbitrary code or delete data irreversibly.
From the tool's definition The tool uploads an expense attachment, creating or storing new data in Sanka's system ('Upload an expense attachment to Sanka from an already available base64 payload').
Attacks that exploit this kind of access
Upload an expense attachment to Sanka from an already available base64 payload. Prefer this direct upload for ordinary receipt/invoice PDFs when the client can pass content_base64 reliably. For client-local PDFs or payloads that are too large or unreliable to pass as one content_base64 string, use start_expense_attachment_upload, append_expense_attachment_upload_chunk until done, then finish_expense_attachment_upload. Use the returned file_id in create_expense or update_expense. Ordinary receipt and invoice PDFs should be uploaded as-is; do not compress or substitute extracted text unless the original upload actually fails. It is categorised as a Write tool in the Sanka MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Sanka MCP Server MCP server in PolicyLayer and add a rule for upload_expense_attachment: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Sanka MCP Server. Nothing to install.
upload_expense_attachment is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the upload_expense_attachment rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for upload_expense_attachment. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
upload_expense_attachment is provided by the Sanka MCP Server MCP server (sankahq/sanka-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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