feat(serve): --compress-tools for MCP tool-description byte-budgeted drop

[Delqhi]

Closes #173

Implements issue #173: add a --compress-tools flag to sin-code serve that shrinks the 47 MCP tool descriptions on the wire, without changing tool names, schemas, or behavior.

What is new

Package cmd/sin-code/internal/mcpcompress/ — ponytail-tag compressor with five canonical Rules:

Tag	Rule	Drops
delete	DeleteHedges	pleasantries / hedge adverbs ("safely", "carefully", ...)
stdlib	StdlibPatterns	redundant (via stdlib) parentheticals; Go stdlib … adjectives
native	DropTrimEncouragement	M6 tail clauses Always prefer over native X / Prefer sin_X over native Y
yagni	YagniPatterns	speculative (experimental) / (TBD) / (reserved) parentheticals
shrink	ShrinkExamples	redundant (e.g. …) / (such as …) parenthetical examples

Three new serve flags:

• --compress-tools — apply default full tag set
• --compress-tags <csv> — comma-separated override (e.g. delete,yagni,shrink)
• --print-stats — emit per-tool byte-budget table to stderr

Byte-stability

Every Rule, the Pipeline, and the post-pipeline Normalize are deterministic and idempotent. The compressor_test.go golden suite pins the wire bytes — prerequisite for the system-prompt hash metric (issue #2). Adding the 6th rule is non-breaking; renaming a tag/rule is a major bump (per AGENTS.md §10).

Tool-name safety

The 47 MCP tool Name fields are public API (AGENTS.md §10) and are NEVER modified. CompressSpec asserts this in TestCompressSpec_NameMutable.

Live JSON-RPC smoke test (47 tools, default tag set)

tool	orig	comp	saved	ratio
sin_execute	80	73	7	8.8%
sin_read	200	167	33	16.5%
sin_write	194	160	34	17.5%
sin_edit	474	441	33	7.0%
TOTAL (47)	3977	3870	107	2.7%

43 other tools' descriptions don't match any conservative pattern and stay byte-identical.

Verification

gofmt -l cmd/sin-code/internal/mcpcompress/                              clean
go build ./...                                                            clean
go vet ./cmd/sin-code/...                                                 clean
go test -race -count=1 ./cmd/sin-code/internal/mcpcompress/ -v            PASS (+ 14 sub-tests)
go test -race ./cmd/sin-code/internal (serve subset)                     PASS
golangci-lint run ./cmd/sin-code/internal/mcpcompress/                   0 issues
govulncheck ./cmd/sin-code/internal/mcpcompress/...                      No vulns
gosec -no-fail -fmt sarif ./cmd/sin-code/internal/mcpcompress/...         clean
python3 scripts/validate_skill.py --all-bundled --strict                 34/34 OK
/tmp/sin-code-test serve --help | grep -- --compress-tools               present

Docs

• AGENTS.md §6 — new mcpcompress/ package listed
• AGENTS.md §8 — (next) → v3.19.0, header bumped to v3.19.0
• AGENTS.md §10 — new Ponytail tag set subsection
• CHANGELOG.md — Unreleased entry with savings table

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Project	Deployment	Actions	Updated (UTC)
sin-code	Ready	Preview, Comment, Open in v0	Jun 16, 2026 7:32pm

[github-actions]

🏆 CEO Audit — A+ (100.0/100)

Metric	Value
Grade	A+
Score	100.0/100
Critical findings	0
High findings	0
Profile	QUICK
Min grade gate	B

📥 Download full report (Markdown)
📊 Download SARIF (for Code Scanning)

Run ~/.config/opencode/skills/ceo-audit/scripts/audit.sh . --profile=QUICK locally to reproduce.

[github-actions]

🏆 CEO Audit — A+ (100.0/100)

Metric	Value
Grade	A+
Score	100.0/100
Critical findings	0
High findings	0
Medium findings	0
Profile	QUICK
Min grade gate	B

📥 Download full report (Markdown)

Run ID: 27642846894 · Commit: ${github.sha}

Run ~/.config/opencode/skills/ceo-audit/scripts/audit.sh . --profile=QUICK locally to reproduce.