majiayu000 GPT-5.2 Spec Writer
Guide for writing prompt specifications tailored for GPT-5.2. The model excels at structured reasoning and instruction following but benefits from explicit constraints on verbosity and scope.
How to Write a Spec
A spec is a markdown document defining persona, constraints, architecture, and operational rules for an agent.
- Start with references/spec-template.md
- Fill in project-specific sections (directive, architecture, conventions)
- Verify coverage: task structure, verbosity/scope constraints, tool usage guidance, context handling for large inputs
Key Patterns
Explicit Task Roadmaps with Checkboxes
Every spec should include an objective, actionable sequence of tasks using markdown checkboxes (- [ ]). GPT-5.2 performs best with concrete work items and clear completion criteria, not abstract guidance.
- Use
- [ ]checkboxes for all tasks—GPT-5.2 tracks and checks them off as work completes - Numbered phases with measurable objectives
- Specific file paths and function names
- Concrete steps: Read X -> Edit Y -> Run Z
- Completion criteria for each task
Example:
- [ ] 1.1 Fix null check in `parse_config()` at line 42
- [ ] 1.2 Add error handling to `load_settings()`
- [ ] 1.3 Run tests and verify all pass
Avoid vague instructions like "improve the code". Be specific: "Fix the null check in parse_config() at line 42".
XML Constraint Blocks
Use XML tags to define distinct rule sets:
<mandatory_execution_requirements>- execution loop (Read -> Edit -> Verify)<verbosity_and_scope_constraints>- output size and scope control<design_freedom>- when new patterns/refactors are acceptable
Chain of Verification
Instruct the model to verify its work: Edit -> Build/check -> Fix -> Report only when complete.
Tool Usage
- Encourage parallel tool use for batch operations (e.g. reading multiple files)
- Require verification after edits (run build, run tests)
Context Management
For large inputs (>10k tokens), use <long_context_handling> to instruct the model to outline key sections, restate constraints, and anchor claims to specific locations.
References
- Spec Template
- GPT-5.2 Model Guide