# `MCP007` List requirements referencing another
{bdg-ref-info}`mcp | tools <mcp:tools>`
{bdg-ref-info}`mcp | query <mcp:query>`
{bdg-ref-info}`mcp | traceability <mcp:traceability>`
> I would like to see which requirements reference or depend on a specific requirement
> to understand dependency chains and impact analysis. When a requirement changes, I need
> to know what other requirements might be affected.
> 

The user shall be able to query which requirements reference a given requirement.

The MCP server shall expose a tool named `list_references_to` that accepts
a requirement ID and returns all requirements that reference it in their `ref` field.

The response shall be a list of requirement summaries, each containing:
- `id`: The unique identifier
- `short`: The short description (if present)
- `category`: The requirement category

The list shall be sorted alphabetically by ID.

If no requirements reference the given ID, an empty list shall be returned.
If the requirement ID does not exist, an error shall be returned.


:::{dropdown} Properties
:icon: note
:color: primary

__author__: Claude

__since__: `0.2.0`

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:::{dropdown} Tested by
:open: 
:icon: check-circle-fill
:color: success

- [`TMCP020` list_references_to returns referencing requirements](/tests/TMCP020)
- [`TMCP021` list_references_to returns empty list for unreferenced requirement](/tests/TMCP021)
- [`TMCP022` list_references_to errors on unknown ID](/tests/TMCP022)
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:::{dropdown} References
:icon: link
:color: secondary

__Relates to:__
[`MCP003` Get requirement by ID](/requirements/MCP003)

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:::{dropdown} Source
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:color: info

__Source file__: [`specs/mcp/tracability.yaml`](https://github.com/agagniere/speky/blob/master/specs/mcp/tracability.yaml)

__Loaded from__: [`speky_mcp`](https://github.com/agagniere/speky/blob/master/specs/mcp/mcp.toml)

__Implemented in:__
{fab}`python` [`handle_list_references_to`](https://github.com/agagniere/speky/blob/master/python/speky_mcp/tools.py#L136)
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