# `TMCP015` search_requirements errors on unknown tag

The user shall receive a tool execution error when filtering by a tag
that does not exist in the loaded specifications.


:::{dropdown} Is a test for
:open: 
:icon: check-circle-fill
:color: primary

[`MCP005` Search and filter requirements](/requirements/MCP005)
:::
:::{dropdown} Automated in
:open: 
:icon: check-circle-fill
:color: success

{fab}`python` [`test_search_unknown_tag`](https://github.com/agagniere/speky/blob/master/tests/test_mcp_server.py#L417)
:::
:::{dropdown} Source
:icon: file-code
:color: info

__Source file__: [`specs/mcp/test_05.yaml`](https://github.com/agagniere/speky/blob/master/specs/mcp/test_05.yaml)

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

:::

## Initial state
The expected state is the final state of
[`TMCP003` Initialize the MCP server](/tests/TMCP003)
## Procedure
### Step 1
The client calls `search_requirements` with a tag that no requirement has
```json
{
  "id": 2,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "name": "search_requirements",
    "arguments": {"tag": "nonexistent"}
  }
}

```
### Step 2
Verify a tool execution error is returned indicating the tag was not found
```json
{
  "id": 2,
  "jsonrpc": "2.0",
  "result": {
    "isError": true,
    "structuredContent": {
      "error": "Tag 'nonexistent' not found"
    }
  }
}

```