---
title: "Tail Dependence"
method: GET
path: "/api/contagion/tail-dependence"
tags: ["contagion"]
---

# Tail Dependence

`GET /api/contagion/tail-dependence`

## Request

- Base URL: `https://basisprotocol.xyz` (the document declares no server; this is the origin it was published from)
- URL: `https://basisprotocol.xyz/api/contagion/tail-dependence`
- Auth: none declared

Return the calibrated lower-tail-dependence λ_L matrix for ``peg_type``.

The first parametric layer over the empirical co-stress counts: per pair, λ_L =
n_joint_tail / min(n_a_tail, n_b_tail) with a Wilson finite-sample band. Reads
the latest run's frozen ``tail_dependence`` rows (written by the slow-cycle
calibration pass), tier1_estimable pairs first then by λ_L desc, wrapped in the
same provenance envelope as ``/pairwise`` (calibration_window /
qualified_entity_count / formula_version from the latest calibration run) plus
the §6 λ_L disclaimer. Pairs below the #355 support floor carry
support_tier='tier2_flagged' with a wide band — reported, never presented as
trustworthy. Pre-calibration (no run / no rows) returns an empty set with a
null envelope.

## Query parameters

- `peg_type` string

## Response `200`

Successful Response

- object

## Other responses

- `422`: Validation Error

---

[API](https://skmtc.dev/basisprotocol/apis/basis-protocol-api.md) · [All operations](https://skmtc.dev/basisprotocol/apis/basis-protocol-api/llms.txt) · [OpenAPI document](https://skmtc.dev/basisprotocol/apis/basis-protocol-api/revisions/c0067366b9c0?raw)