Submit a new bill to the accounts payable system, requiring confirmation for amounts over 25,000.
Create a bill. Bills over 25,000 ask the user to confirm first.
| Name | Required | Description | Default |
|---|---|---|---|
| qty | Yes | Quantity | |
| po_id | No | Purchase order id, if any | |
| due_date | Yes | YYYY-MM-DD | |
| vendor_id | Yes | Vendor id | |
| unit_price | Yes | Unit price | |
| invoice_date | Yes | YYYY-MM-DD | |
| invoice_number | Yes | Invoice number from the vendor |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full behavioral burden. It helpfully discloses the >25,000 confirmation threshold, a genuinely useful interaction rule, but says nothing about side effects (record creation), permissions, or whether repeated invoice numbers are rejected.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Two sentences, both earning their place: the first establishes the action, the second front-loads the one non-obvious behavioral constraint. No filler whatsoever.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a 7-parameter mutation with no annotations and no output schema, the description is thin. It omits what the tool returns (bill id?), whether the bill is created in draft/pending state, and how errors like duplicate invoice numbers are handled.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%, so all 7 parameters are already documented in the schema with dates, ids, and quantity/price labels. The description adds no additional parameter meaning, which is the baseline expectation when the schema does the work.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
States a specific verb and resource ('Create a bill'), which is unambiguous, but it offers no differentiation from siblings like match_invoice or request_payment_release and does not clarify scope (single bill, required fields).
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The tool's purpose implies when it is used, and the description adds a conditional workflow rule (confirmation above 25,000). However, it names no alternatives and gives no guidance on prerequisites such as whether a vendor or PO must already exist.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.