Long prompt, unstable output
Rules, evidence and task instructions compete in the same unstructured block.
BUILD RELIABLE AI APPLICATIONS
Context Engineering Tutorial and System Design
A longer prompt will not fix stale retrieval, noisy memory or overloaded tools. Learn to give the model the right evidence at the right step — with a budget, trace and evaluation gate.
10 chapters8 core gatesContext System Spec
context.build()TRACE ON
system_policystable
toolslazy
memoryscoped
evidencereranked
user_taskcurrent
SELECT
→BUDGET
→EVAL
If the output changes for no clear reason, the context system is already the product problem
These failures often look like model problems. They are usually selection, ordering, memory or permission problems.
The right document was retrieved
The model still follows a louder distractor or misses evidence in the middle.
History keeps growing
Old decisions and stale facts enter every turn without an expiry or write policy.
Tools drown the task
Schemas consume attention while permissions and failure boundaries stay implicit.
Context is a system, not one long prompt
Five sources enter the call. Selection and budget decide what survives. Trace and evaluation decide whether the system is safe to release.
System policy
Stable rules, identity and non-negotiable boundaries.
Tool contracts
Only the capabilities required for this step, with permission limits.
Memory
Session state and durable facts with lifecycle rules.
Retrieved evidence
Fresh, attributable passages selected for the current question.
User task
The immediate request, constraints and definition of done.
Eight gates produce one Context System Spec
Use one real assistant, RAG flow or agent throughout the track. Every chapter adds reviewable evidence to the same system specification.
01 · Boundary
Problem and success contract
Complete this artifact inside the chapter workspace.
02 · InventoryFive-layer context map
Complete this artifact inside the chapter workspace.
03 · SelectInclusion and exclusion rules
Complete this artifact inside the chapter workspace.
04 · BudgetToken allocation and ordering
Complete this artifact inside the chapter workspace.
05 · GroundRetrieval and rerank evidence
Complete this artifact inside the chapter workspace.
06 · RememberMemory lifecycle policy
Complete this artifact inside the chapter workspace.
07 · ActTool permission contract
Complete this artifact inside the chapter workspace.
08 · EvaluateEval set and release record
Complete this artifact inside the chapter workspace.
Ten chapters, organised around the decisions you must make
Follow the core gates in order. The tool comparison and agent chapters extend the design after the foundation is stable.
STAGE 01
Frame the system
Separate the task from the context that supports it.
STAGE 02
Control evidence and cost
Allocate space, retrieve broadly and select deliberately.
STAGE 03
Design memory and action
Control what persists and which tools can act.
STAGE 04
Compare and validate
Inspect real agent strategies, then validate your own system.
Context System Spec
Leave with a system another engineer can inspect
The finished spec explains what enters context, why it is trusted, how much space it receives, what can act, and how failures are detected.
System boundary
Context source register
Selection rules
Token budget
Memory policy
Tool permission map
Trace schema
Evaluation and release gate