REI Crypto MCP Server

get_yield_chart_lend_borrow

Retrieve historical borrow cost APY data from lending market pools to analyze borrowing trends and costs over time.

Instructions

GET /yields/chartLendBorrow/{pool}

Historical borrow cost APY from a pool on a lending market.

Parameters:
    pool: pool id (can be retrieved from /poolsBorrow)

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "pool": "<pool>"
    },
    "name": "get_yield_chart_lend_borrow"
  }
}

Input Schema

Name	Required	Description	Default
`pool`	Yes

Output Schema

Name	Required	Description	Default
`result`	Yes

Implementation Reference

defillama_server.py:362-372 (handler)

The main handler function for the 'get_yield_chart_lend_borrow' tool. It is registered via the @mcp.tool() decorator and fetches historical borrow cost APY data from the DefiLlama API for a given pool ID, returning the JSON response as a string.

@mcp.tool()
async def get_yield_chart_lend_borrow(pool: str) -> str:
    """GET /yields/chartLendBorrow/{pool}
    
    Historical borrow cost APY from a pool on a lending market.
    
    Parameters:
        pool: pool id (can be retrieved from /poolsBorrow)
    """
    result = await make_request('GET', f'/yields/chartLendBorrow/{pool}')
    return str(result)

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedv1.0.0Jan 2, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "result": {
+      "title": "Result",
+      "type": "string"
+    }
+  },
+  "required": [
+    "result"
+  ],
+  "title": "get_yield_chart_lend_borrowOutput",
+  "type": "object"
+}

First observedMay 11, 2025

TDQS

B3.3/5.0

Behavior2/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are provided, so the description carries the full burden. It states it's a GET operation for historical data, implying read-only behavior, but doesn't disclose other traits like rate limits, authentication needs, error handling, or what 'historical' entails (e.g., time range, granularity). The description is minimal and lacks behavioral details beyond the basic operation.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is appropriately sized and front-loaded, starting with the endpoint and core purpose. The two sentences are efficient, with no wasted words. However, the structure could be slightly improved by integrating the parameter note more seamlessly, but it remains clear and concise overall.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool has an output schema (which reduces the need to describe return values) and no annotations, the description is moderately complete. It covers the purpose and parameter semantics adequately but lacks behavioral transparency and usage guidelines relative to siblings. For a tool with historical data retrieval, more context on data scope and limitations would enhance completeness.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, so the description must compensate. It adds meaningful context for the single parameter 'pool', explaining it's a pool ID and can be retrieved from '/poolsBorrow'. This clarifies the parameter's purpose and source, though it doesn't detail format constraints (e.g., string pattern) or provide examples.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool's purpose: retrieving historical borrow cost APY from a specific pool on a lending market. It specifies the verb ('GET'), resource ('/yields/chartLendBorrow/{pool}'), and scope ('historical borrow cost APY'). However, it doesn't explicitly differentiate from sibling tools like 'get_yield_chart' or 'get_yield_pools_borrow', which appear related but have different focuses.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies usage context by mentioning that the pool parameter can be retrieved from '/poolsBorrow', which suggests a prerequisite. However, it doesn't provide explicit guidance on when to use this tool versus alternatives (e.g., 'get_yield_chart' or 'get_yield_pools_borrow'), nor does it specify exclusions or ideal scenarios for its use.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Deploy Server