"What does paper [DOI] cite" / "references in [paper]" / "what sources does this paper use" — DOIs cited BY the given DOI (the paper's reference list / bibliography). Use for citation-graph traversal, literature review, source tracking.
Part of the Opencitations server.
Free to start. No card required.
AI agents call references to retrieve information from Opencitations without modifying any data. This is common in research, monitoring, and reporting workflows where the agent needs context before taking action. Because read operations don't change state, they are generally safe to allow without restrictions -- but you may still want rate limits to control API costs.
Even though references only reads data, uncontrolled read access can leak sensitive information or rack up API costs. An agent caught in a retry loop could make thousands of calls per minute. A rate limit gives you a safety net without blocking legitimate use.
Read-only tools are safe to allow by default. No rate limit needed unless you want to control costs.
{
"version": "1",
"default": "deny",
"tools": {
"references": {}
}
}See the full Opencitations policy for all 26 tools.
These attack patterns abuse exactly the kind of access references gives an agent. Each links to the full case and the policy that stops it:
Other read tools across the catalogue. The same approach applies to each: allow, with a rate cap to control cost.
"What does paper [DOI] cite" / "references in [paper]" / "what sources does this paper use" — DOIs cited BY the given DOI (the paper's reference list / bibliography). Use for citation-graph traversal, literature review, source tracking.. It is categorised as a Read tool in the Opencitations MCP Server, which means it retrieves data without modifying state.
Register the Opencitations MCP server in PolicyLayer and add a rule for references: 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 Opencitations. Nothing to install.
references 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 references 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 references. 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.
references is provided by the Opencitations MCP server (https://gateway.pipeworx.io/opencitations/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 26 Opencitations tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
4,600+ MCP servers and 31,000+ tools scanned and risk-classified.