| name | add-mcp-tool |
| description | Add a new MCP tool to the Context Keeper server. Use when adding a tool, implementing a new MCP capability, or extending the server's tool surface. |
Add MCP Tool
Steps
1. Define the Input Schema
In crates/context-keeper-mcp/src/tools.rs, add a new input struct near the other *Input types:
#[derive(Debug, Deserialize, schemars::JsonSchema)]
pub struct MyToolInput {
#[schemars(description = "Description shown to MCP clients")]
pub field: String,
#[schemars(description = "Optional field with default behavior")]
pub limit: Option<usize>,
}
Every field needs a #[schemars(description)] — this is what the MCP client sees.
2. Define the Response Type (if needed)
Add a #[derive(Debug, Serialize)] struct if the response has structure beyond a simple string.
3. Implement the Tool Method
Add the method inside the #[tool_router] impl ContextKeeperServer block:
#[tool(description = "One-sentence description for the MCP tool listing")]
async fn my_tool(
&self,
Parameters(input): Parameters<MyToolInput>,
) -> Result<String, McpError> {
serde_json::to_string_pretty(&result)
.map_err(|e| McpError::internal_error(format!("Serialization failed: {e}"), None))
}
4. Update Server Instructions (if significant)
If the tool adds a new capability category, update the instructions string in get_info() at the bottom of tools.rs.
5. Test
cargo build -p context-keeper-mcp
cargo test -p context-keeper-mcp
Then test with an MCP client (Claude Desktop, Cursor, or mcp-cli).
Checklist
