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STEP 26 / 27

B1 TOOL-SCHEMA

DEFINE THE SCHEMA

Write the JSON Schema for the inventory_mcp tool.

TOOL PURPOSE

Design a complete 3-tool MCP so an agent can manage the ship's critical
parts inventory. The agent will use it for requests like:

- "how many bay regulators do we have left?"
- "mark the bay 3 charger as low-stock"
- "add 12 H7-type air filters to the inventory"

Three minimum tools to cover the case:

1. `list_inventory_items(category?)`. read. Lists items with their stock.
   category is optional, to filter (e.g. "regulator", "filter", "charger").
2. `add_inventory(item_id, quantity, location)`. write. Adds units to
   an existing item. Returns the new total.
3. `mark_item_low_stock(item_id, reason)`. write. Marks an item as
   requiring re-supply. reason is free-form text (the reason for the alert).

Your job: the complete JSON with all 3 definitions. The descriptions
must be good enough that an agent picks them correctly without you
having to orient the conversation.

EXAMPLE INVOCATIONS

list_inventory_items(category: "regulator") → {items: [{item_id: "reg-bay-001", name: "...", stock: 4, location: "vault-A"}, ...]}
add_inventory(item_id: "filter-H7", quantity: 12, location: "vault-A") → {ok: true, new_stock: 28}
mark_item_low_stock(item_id: "charger-bay-3", reason: "Intermittent failure, replace before next cycle") → {ok: true}

YOUR SCHEMA

585 CHARACTERS

9 CRITERIA

GUEST MODE

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Your first complete MCP

So far every tool has been an isolated case. The capstone is the whole MCP: 3 tools covering a domain (critical parts inventory), designed so an agent picks them by itself, without extra instructions from the user.

The scenario

Forge has a record of critical replacement parts. She wants an agent to be able to:

Query the stock. "how many regulators are left?"
Restock items. "add 12 H7 filters to vault-A"
Mark items for re-supply. "the bay 3 charger is failing, mark it low-stock"

Three tools cover the whole domain. Your job: design the full MCP JSON Schema, with descriptions precise enough that the agent knows which one to use for each request, without you having to orient the conversation.

What has to be right

8 criteria. the first 5 deterministic (structure, correct required), the last 3 LLM-judge over the quality of the descriptions:

Valid JSON.
The 3 tools defined.
list_inventory_items.category is optional (NOT in required).
add_inventory has 3 required.
mark_item_low_stock has 2 required.
Descriptions distinguish read vs write.
At least one description says when NOT to use the tool.
At least one description mentions the chained usage pattern.
All parameters have a description.

How everything from the track applies

Unit	Skill	How it shows up here
1 · What a tool is	The 3 tools have name + description + parameters
2 · Schema craft	Clear names, correct required, enums where they apply, documented outputs
3 · Descriptions the LLM reads	Criteria 6, 7 and 8: read vs write, when NOT to use, composition hint
4 · Production handlers	Applies to the real handler (not this schema). Think idempotency: `add_inventory` called 2× should add 2×, not 1×. And actionable error messages.
5 · Composition and catalog	Criterion 8: the `list_inventory_items` → `mark_item_low_stock` pattern has to be suggested
6 · State, scope, debugging	Think: what scope does each tool need? `list` is read-only, the other two modify state. Does the agent have write authorization?

If your MCP passes the 9 deterministic and judge criteria, you can trust an agent will use it well without you having to babysit every conversation.

When you pass, Forge signs your first MCP. You're cleared to design real tools. the ones used in production, not in demos.