Find a packaged food by barcode.
Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.
{
"id": 1,
"jsonrpc": "2.0",
"method": "tools/call",
"params": {
"arguments": {
"barcode": "<barcode>"
},
"name": "lookup_food_barcode"
}
}| Name | Required | Description | Default |
|---|---|---|---|
| barcode | Yes |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The readOnlyHint annotation already covers the safety profile, but the description adds nothing beyond it: no accepted barcode symbologies (UPC-A/EAN-13), no behavior when the barcode is unregistered, and no indication of the shape of the returned record — notable since there is no output schema.
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?
A single front-loaded sentence with no filler, and the resource is stated first. It is efficient, though its brevity reflects under-specification rather than disciplined restraint.
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 lookup tool with no output schema and 0% parameter coverage, the description should describe at minimum the expected input format and what a successful or failed lookup returns. Neither is present, so the agent is left guessing on the two things that matter most.
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?
Only one parameter with 0% schema description coverage, so the description must carry the format semantics. It does not say whether the barcode should be digits-only, whether hyphens or spaces are tolerated, or how it relates to the schema's minLength of 4.
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 ('Find') and resource ('packaged food by barcode'), which is unambiguous on its own and distinguishable from the free-text sibling search_foods. It stops short of naming or contrasting that sibling explicitly.
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?
No statement of when to prefer this over search_foods, no exclusion (e.g., 'use when you have a scannable barcode, not a dish name'), and no guidance for the not-found or unrecognized-barcode case. The agent must infer that this is the barcode-exact-lookup path.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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