discover_tool

discover_tool is how the agent looks up the full schema of an upstream tool before calling it with use_tool.

Description (dynamic)

The description shown to the host is generated at runtime from the upstream tool catalog. It opens with a one-line instruction and follows with the full catalog wrapped in a <tools> XML block. Each MCP is a named group with its tools as a bullet list.

When dynamic discovery is on, the description also includes a <mcp_servers> block listing every upstream MCP that hasn’t been loaded yet, along with the description you wrote for each.

Single MCP mode

No namespace prefix on tool names:

Use this tool to look up the full schema of a tool before calling it with use_tool.
Call discover_tool with a tool name from the list below to get its complete description,
input parameters, and output schema. Always discover a tool before using it.

<tools>
- browser_navigate: Navigate the browser to a URL
- browser_screenshot: Take a screenshot of the current page
- browser_click: Click an element on the page
</tools>

Config file mode

Tools are grouped under their MCP name. To call a tool, combine the group header with the bullet — chrome-devtools + browser_navigate → chrome-devtools/browser_navigate.

Use this tool to look up the full schema of a tool before calling it with use_tool.
Call discover_tool with a tool name from the list below to get its complete description,
input parameters, and output schema. Always discover a tool before using it.

<tools>
chrome-devtools:
- browser_navigate: Navigate the browser to a URL
- browser_screenshot: Take a screenshot of the current page
- browser_click: Click an element on the page

filesystem:
- read_file: Read the contents of a file
- write_file: Write content to a file
</tools>

Dynamic discovery mode

<mcp_servers> shows MCPs that haven’t been loaded yet. <tools> shows only what’s currently loaded (eager MCPs and any lazy MCPs the agent has already loaded).

Use this tool to look up the full schema of a tool before calling it with use_tool.
Call discover_tool with a tool name from the list below to get its complete description,
input parameters, and output schema. Always discover a tool before using it.

Some MCP servers below are not loaded yet and are listed under <mcp_servers> with a
short description of what they do. To make a server's tools (and any resources or
prompts it exposes) available, call load_mcp with its name. Once loaded, the server's
tools will appear in the <tools> list and become callable via use_tool. Loading is
permanent for the remainder of this session.

<mcp_servers>
- chrome-devtools: Browser automation via Chrome DevTools Protocol. Navigate pages,
  take screenshots, inspect the DOM, run JavaScript in page context, capture network
  traffic. Use when you need to interact with a live web page.
- jira: Read and write Jira issues, comments, transitions, and sprint state. Use when
  the task involves tracking work or referencing tickets.
</mcp_servers>

<tools>
filesystem:
- read_file: Read the contents of a file
- write_file: Write content to a file
</tools>

If dynamic discovery is on and nothing is loaded yet (no eager MCPs, no successful load_mcp calls), the <tools> block is dropped and a closing line tells the agent that no tools are currently loaded.

Input

Field	Type	Description
tool_name	string	The name of the upstream tool to look up. Bare name in single-MCP mode (e.g. browser_navigate); namespaced in config file mode (e.g. chrome-devtools/browser_navigate).

Output

The full tool schema:

• Tool name as exposed in the current mode (bare in single-MCP mode, namespaced in config-file mode).
• Complete description.
• Input schema: parameter names, types, descriptions, required flags.

Errors

If tool_name doesn’t match any proxied tool, discover_tool returns a clear error listing the names that are available.