Mcp Lazarus Pascal Reference Documentation
Mcp
Current Version: 11.6.0
Chilkat.Mcp
Read resources with
Pass a connected A client for the Model Context Protocol (MCP).
Chilkat.Mcp connects to an MCP server and gives an application access to the
server's tools, resources, and prompts
over a single, unified API. MCP is an open protocol that standardizes how applications
supply context and callable tools to AI models.
Connect & handshake
Connect opens a Streamable HTTP session and performs
the MCP initialize handshake, negotiating the protocol version and
establishing a session id.
Resources & prompts
ListResources and
ReadResource, and fetch prompts with
ListPrompts and
GetPrompt.
Use with Chilkat.Ai
Chilkat.Mcp to Chilkat.Ai.UseMcp to register the
server's tools with an AI model. During a conversation the model's tool calls are
routed to the MCP server automatically.
Streamable HTTP transport
(protocol version 2025-06-18). A server response may arrive as a single JSON
object or as a Server-Sent-Events stream; both are handled transparently. The stdio
transport is not supported.
AuthToken property before calling
Connect. Chilkat then sends it as an
Authorization: Bearer <token> header on every request. Leave it
unset for servers that do not require authentication.
tools/list, resources/list, and prompts/list
results include a nextCursor string. In this release the list methods
return the first page only and do not accept a cursor argument, so nextCursor
is informational.
Create / Free
uses
Chilkat.Mcp;
var
obj: TMcp;
begin
obj := TMcp.Create;
try
if not obj.IsValid then
raise Exception.Create('Failed to create a TMcp instance.');
// ... use obj ...
finally
obj.Free;
end;
end;
Allocates the underlying CkMcp object and returns a new TMcp instance. Simply adding Chilkat.Mcp to the unit's uses clause is enough to locate and bind to the Chilkat shared library (DLL / .so / .dylib) at runtime — no separate load step is required. Check obj.IsValid after calling Create; it is False if the underlying library could not be found/loaded or the object could not be allocated (for example, when unlicensed).
Every TMcp created by calling Create should eventually be released by calling .Free (inherited from TObject). The destructor automatically disposes the underlying CkMcp handle. A native (unmanaged) memory leak occurs if the object is never freed.
Properties
AuthToken
An optional bearer token for authenticating to the MCP server. When set, it is sent as an Authorization: Bearer <token> header on every request. The default is the empty string.
Connected
ConnectTimeoutMs
The maximum amount of time, in milliseconds, to wait to establish the TCP/TLS connection to the MCP server. The default value is 30000 (30 seconds).
DebugLogFilePath
If set to a file path, this property logs the LastErrorText of each Chilkat method or property call to the specified file. This logging helps identify the context and history of Chilkat calls leading up to any crash or hang, aiding in debugging.
Enabling the VerboseLogging property provides more detailed information. This property is mainly used for debugging rare instances where a Chilkat method call causes a hang or crash, which should generally not happen.
Possible causes of hangs include:
- A timeout property set to 0, indicating an infinite timeout.
- A hang occurring within an event callback in the application code.
- An internal bug in the Chilkat code causing the hang.
HeartbeatMs
The interval in milliseconds between each AbortCheck event callback, which enables an application to abort a method before it completes. By default, HeartbeatMs is 0, meaning no AbortCheck event callbacks fire.
IdleTimeoutMs
The maximum amount of time, in milliseconds, to wait for additional incoming data when receiving a response has paused. This is not a total timeout. The default value is 180000 (180 seconds).
LastErrorHtml
Provides HTML-formatted information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.
topLastErrorText
Provides plain text information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.
LastErrorXml
Provides XML-formatted information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.
topLastMethodSuccess
Indicates the success or failure of the most recent method call: True means success, False means failure. This property remains unchanged by property setters or getters. This method is present to address challenges in checking for null or Nothing returns in certain programming languages. Note: This property does not apply to methods that return integer values or to boolean-returning methods where the boolean does not indicate success or failure.
ProtocolVersion
The MCP protocol version. May be set before Connect to request a specific version; after Connect it reflects the version negotiated with the server and is sent in the MCP-Protocol-Version header of each request. The default is 2025-06-18.
ServerInstructions
Read-only. Optional usage instructions provided by the server in the initialize result (may be the empty string), available after Connect.
ServerName
ServerVersion
SessionId
Read-only. The Mcp-Session-Id assigned by the server during the Connect handshake, or the empty string if the server is stateless. Chilkat automatically includes this session id on all subsequent requests.
VerboseLogging
If set to True, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. The default value is False. Verbose logging should only be used for debugging. The potentially large quantity of logged information may adversely affect peformance.
Version
Methods
CallTool
// result is a TJsonObject object.
function CallTool(const name: string;
arguments: TChilkatBase;
result: TChilkatBase): Boolean;
Calls the MCP tools/call method for the tool named name, passing the JSON arguments object in arguments. The members of arguments are the tool's input arguments and should match the tool's inputSchema as returned by ListTools. For example, a weather tool might be called with the arguments { "location": "Boston, MA", "units": "fahrenheit" }. Pass an empty JSON object (not a null) for a tool that takes no arguments.
On success, the tool result is placed in result. It contains a content array, an isError boolean, and optionally a structuredContent object. Each element of the content array has a type ("text", "image", "audio", or "resource"); for a "text" element the value is in its text member. A typical result looks like:
{
"content": [ { "type": "text", "text": "The weather in Boston is 72F and sunny." } ],
"isError": false
}
Thus the text of the first content item is at JSON path content[0].text.
Note: A tool that executes but reports a failure returns True here with isError set to True in result (the failure message is typically carried in the content array). The return value is False only for transport- or protocol-level failures.
Connect must be called first.
Returns True for success, False for failure.
Close
Explicitly terminates the MCP session by sending an HTTP DELETE with the Mcp-Session-Id header, then releases the connection. It is safe to call this method when not connected (it simply releases any transport). A server that does not permit client-terminated sessions responds with HTTP 405, which is not treated as an error.
Returns True for success, False for failure.
Connect
Connects to the MCP (Model Context Protocol) server at the Streamable HTTP endpoint URL in url (for example https://example.com/mcp) and performs the MCP initialize handshake.
On success, the SessionId, ProtocolVersion, ServerName, ServerVersion, and ServerInstructions properties are populated, and Connected becomes True.
If an AuthToken is set, it is sent as a bearer token on the request. The URL must begin with http:// or https://; the host, port, and path are taken from it. Only the Streamable HTTP transport is supported; the stdio transport is not.
Returns True for success, False for failure.
GetLastJsonData
procedure GetLastJsonData(json: TChilkatBase);
Returns, in json, the complete JSON-RPC response envelope from the most recent request (the jsonrpc, id, and result or error members), for diagnostics and logging. Note that this is the full JSON-RPC envelope, whereas ListTools, CallTool, ReadResource, and GetPrompt each return only the inner result object.
GetPrompt
// json is a TJsonObject object.
function GetPrompt(const name: string;
arguments: TChilkatBase;
json: TChilkatBase): Boolean;
Calls the MCP prompts/get method for the prompt named name, passing the JSON arguments object in arguments (pass an empty object for a prompt that takes no arguments). On success, the result is placed in json, consisting of an optional description and a messages array in which each message has a role and content.
Connect must be called first.
Returns True for success, False for failure.
ListPrompts
function ListPrompts(json: TChilkatBase): Boolean;
Calls the MCP prompts/list method. On success, the server's result object is placed in json, containing a prompts array in which each prompt has a name, optionally a description, and an arguments array, and possibly a nextCursor for pagination.
Connect must be called first.
Returns True for success, False for failure.
ListResources
function ListResources(json: TChilkatBase): Boolean;
Calls the MCP resources/list method. On success, the server's result object is placed in json, containing a resources array in which each resource has a uri, a name, and optionally a description and mimeType, and possibly a nextCursor for pagination.
Connect must be called first.
Returns True for success, False for failure.
ListTools
function ListTools(json: TChilkatBase): Boolean;
Calls the MCP tools/list method. On success, the server's result object is placed in json, containing a tools array in which each tool has a name, a description, and an inputSchema (a JSON Schema describing the tool's arguments), and possibly a nextCursor for pagination.
Connect must be called first.
Returns True for success, False for failure.
ReadResource
function ReadResource(const uri: string;
json: TChilkatBase): Boolean;
Calls the MCP resources/read method for the resource identified by the URI in uri. On success, the result is placed in json, containing a contents array whose entries carry a uri, a mimeType, and either text (for text resources) or blob (base64 for binary resources).
Connect must be called first.
Returns True for success, False for failure.
SetConnectionSettings
function SetConnectionSettings(sock: TChilkatBase): Boolean;
Copies connection settings, including HTTP proxy, SOCKS proxy, bind (network interface) IP address, and TLS options, from sock. This is optional; if not used, default settings apply. Call this method before Connect.
Returns True for success, False for failure.
Events
Chilkat for Pascal supports three synchronous event callbacks: OnAbortCheck, OnPercentDone, and OnProgressInfo. Each is a property of the class; assign a method of one of your own objects (an of object handler) to receive the callbacks, or assign nil to unhook. The handler types are declared in the Chilkat.Base unit:
TChilkatAbortCheckEvent = function(Sender: TChilkatBase): Boolean of object;
TChilkatPercentDoneEvent = function(Sender: TChilkatBase; PctDone: Integer): Boolean of object;
TChilkatProgressInfoEvent = procedure(Sender: TChilkatBase; const Name, Value: string) of object;All Chilkat methods are synchronous, so callbacks are invoked on the thread that called the method -- if the method was called from the main thread, it is safe to access UI elements from the handler. The HeartbeatMs property controls the frequency of OnAbortCheck callbacks (the default of 0 means no AbortCheck events fire). Returning True from an OnAbortCheck or OnPercentDone handler aborts the running method.
AbortCheck
property OnAbortCheck: TChilkatAbortCheckEvent;
Enables a method call to be aborted by triggering the AbortCheck event at intervals defined by the HeartbeatMs property. If HeartbeatMs is set to its default value of 0, no events will occur. For instance, set HeartbeatMs to 200 to trigger 5 AbortCheck events per second.
Event callback implementation:
// A handler is a method of one of your own classes, e.g. a form:
function TMyObject.McpAbortCheck(Sender: TChilkatBase): Boolean;
begin
// Called every HeartbeatMs milliseconds while a method is running.
// Return True to abort the method; return False to continue.
Result := False;
end;To add an event handler:
mcp := TMcp.Create;
mcp.HeartbeatMs := 250; // fire OnAbortCheck 4 times per second
mcp.OnAbortCheck := MyObject.McpAbortCheck;PercentDone
property OnPercentDone: TChilkatPercentDoneEvent;
This provides the percentage completion for any method involving network communications or time-consuming processing, assuming the progress can be measured as a percentage. This event is triggered only when it's possible and logical to express the operation's progress as a percentage. The pctDone argument will range from 1 to 100. For methods that finish quickly, the number of PercentDone callbacks may vary, but the final callback will have pctDone equal to 100. For longer operations, callbacks will not exceed one per percentage point (e.g., 1, 2, 3, ..., 98, 99, 100).
The PercentDone callback also acts as an AbortCheck event. For fast methods where PercentDone fires, an AbortCheck event may not trigger since the PercentDone callback already provides an opportunity to abort. For longer operations, where time between PercentDone callbacks is extended, AbortCheck callbacks enable more responsive operation termination.
To abort the operation, set the abort output argument to True. This will cause the method to terminate and return a failure status or corresponding failure value.
Event callback implementation:
// A handler is a method of one of your own classes, e.g. a form:
function TMyObject.McpPercentDone(Sender: TChilkatBase; PctDone: Integer): Boolean;
begin
// PctDone ranges from 1 to 100.
WriteLn('Percent done: ', PctDone);
// Return True to abort the method; return False to continue.
Result := False;
end;To add an event handler:
mcp := TMcp.Create;
mcp.OnPercentDone := MyObject.McpPercentDone;ProgressInfo
property OnProgressInfo: TChilkatProgressInfoEvent;
This event callback provides tag name/value pairs that detail what occurs during a method call. To discover existing tag names, create code to handle the event, emit the pairs, and review them. Most tag names are self-explanatory.
Note: Some Chilkat methods don't fire any ProgressInfo events.
Event callback implementation:
// A handler is a method of one of your own classes, e.g. a form:
procedure TMyObject.McpProgressInfo(Sender: TChilkatBase; const Name, Value: string);
begin
WriteLn(Name, ': ', Value);
end;To add an event handler:
mcp := TMcp.Create;
mcp.OnProgressInfo := MyObject.McpProgressInfo;