Abstract skill vs. concrete Rust MCP server
"Engineering coworker" names two real, different things in this operator's ecosystem. Conflating them would misrepresent both, so this site keeps them on separate fact_kind values (skill_capability / real_implementation / tool) rather than merging them into one undifferentiated description.
| Axis | Abstract Cowork skill | Concrete Rust MCP server |
|---|---|---|
| What it is | A SKILL.md-defined agent persona: anthropic-skills:engineering-coworker, part of a 7-coworker system in the sister knowledge-engineering repo | crates/engineering-coworker in this repo -- a compiled Rust binary (rmcp, stdio transport) |
| Model | claude-haiku-4-5-20251001 (mechanical implementation tasks) | N/A -- it's a tool server invoked BY a Claude session, not itself a model-backed agent |
| Interaction pattern | Reads/writes JSONL queue (cowork/data/queues/engineering.jsonl) and mailbox (cowork/data/mailbox/engineering-coworker.jsonl) | Exposes MCP tools (cargo_check, cargo_test, wrangler_deploy, d1_query, git_status, git_commit_push) over stdio |
| Purpose | Claims and executes tasks from a durable queue, following hard invariants (no API keys, Conventional Commits, no half-implementations) | Lets Claude cloud (a session like this one) EXECUTE real operations on the developer's own Mac -- not just suggest code |
| Real surfaces | coworkers.subagentknowledge.com/engineering, cowork.subagentknowledge.com | macos__desktop_cowork__engineering_coworker / cloud__docker_mcp__engineering_coworker (this repo's naming ontology) |
Why both are grounded here, not invented
The skill_capability rows were extracted directly from the live anthropic-skills:engineering-coworker skill content, read in full via the Skill tool during this site's build -- its <coworker_identity>, <hard_invariants>, <task_contract>, and <queue_format>/<mailbox_format> blocks. The real_implementation and tool rows come from this repo's own CLAUDE.md, under its "engineering-coworker MCP server (crates/engineering-coworker)" section -- already-shipped, already-documented infrastructure, not written for this task.
Neither source was extrapolated beyond what it actually says: the abstract skill's model is documented as Haiku 4.5, not upgraded to Fable 5 here (that upgrade applies to the agent definition for this role, tracked separately on subagentcode.com's agt_engineering-coworker row, which is a third, distinct axis -- see subagentroles.com's role-vs-identity concept page for how Role, Identity, and Agent Definition relate).
See the homepage for the live 13-row board.