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MCP Tool Call Flow: Specification → SDK → Server

How a tool call flows through the Model Context Protocol, traced across the specification, TypeScript SDK, and reference server implementations.

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Phase 1: Capability Negotiation (Initialization)

During initialize, the server declares it supports tools:

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Comparative Critique: MCP Tool Call Flow Research Reports

Two research reports trace how a tool call flows through the Model Context Protocol. This critique compares their depth, quality, and gaps.

Dimension	Report A (mcp-tool-call-flow.md)	Report B (how-does-a-tool-call-flow...)
Length	~450 lines	~700 lines (~32KB)
Structure	Phase-based (4 phases)	Layer-based (4 layers, 9 numbered steps)
Session	27ed82ad	f349ea56

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Keybase proof

I hereby claim:

• I am terrhorn on github.
• I am terrhorn (https://keybase.io/terrhorn) on keybase.
• I have a public key whose fingerprint is DD56 9F81 4C96 C469 082E F882 3FF5 8ABD DDFB BAC5

To claim this, I am signing this object:

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val collectionName = "my_event_collection"  // the name of your collection
val events = ArrayBuffer.empty[String]  // an array buffer to hold all of the events that we'll batch

// populate the array with 5000 fake events
for(i <- 1 to 5000) {
  events.append(s"""{"foo": { "count": $i, "bar": "baz"} }""")
}

// split events into 5 batches of 1000 events, and send each batch to Keen
for(batch <- events.grouped(1000)) {

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require 'dotenv'
require 'keen'

Dotenv.load

# allow timeframe to be specified via the command line
# usage: ruby collection_counts.rb previous_7_days
if !ARGV[0].nil?
	timeframe = ARGV[0]
end