AI agents call list_sources to retrieve information from Project Tessera without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool queries metadata about indexed documents in the vector store and returns a list. It performs no write, delete, execution, or financial operations. The blast radius of misuse is minimal—an agent could learn what sources exist in the workspace memory, but cannot access their contents, modify them, or trigger external actions. This is a straightforward Read operation.
From the tool's definition Tool name is 'list_sources' and description states it 'List all indexed source files' — a pure retrieval operation with no modification or side effects.
Documented attack patterns abuse exactly the kind of access list_sources gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Project Tessera, and nothing reaches the server without passing your rules. This is the rule we recommend for list_sources:
{
"version": "1",
"default": "deny",
"tools": {
"list_sources": {}
}
}list_sources is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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List all indexed source files. It is categorised as a Read tool in the Project Tessera MCP Server, which means it retrieves data without modifying state.
Register the Project Tessera MCP server in PolicyLayer and add a rule for list_sources: 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 Project Tessera. Nothing to install.
list_sources is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the list_sources 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 list_sources. 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.
list_sources is provided by the Project Tessera MCP server (besslframework-stack/project-tessera). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Project Tessera, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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43 Project Tessera tools catalogued and risk-classified — across an index of 43,000+ MCP servers.