Find pet by ID. - Returns a single pet.
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": {
"petId": "<petId>"
},
"name": "getPetById"
}
}| Name | Required | Description | Default |
|---|---|---|---|
| petId | Yes | ||
| x-hapi-auth-state | No |
Changes observed during successful MCP inspections.
Input schema / properties / petId / descriptionRemoved value: -"ID of pet to return"Input schema / properties / petId / formatAdded value: +"int64"Input schema / properties / petId / typePrevious value: -"string"New value: +"integer"Input schema / requiredAdded value: +[
+ "petId"
+]Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full burden of behavioral disclosure. It only states that it returns a single pet, but does not disclose error behavior (e.g., 404 if not found), authentication needs, or any side effects. This is a minimal disclosure for a tool that could fail in expected ways.
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?
The description is two short sentences, 'Find pet by ID.' and 'Returns a single pet.', both of which add essential information without redundancy. It is front-loaded with the action and provides a clear outcome statement.
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 simple get-by-ID tool with no output schema and no annotations, the description is underspecified. It does not mention error responses, prerequisites, or any constraints. A complete description should at least alert to possible failure modes (e.g., pet not found) to help the agent handle results.
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 0%, so the description must compensate. It implies that 'petId' is the identifier used for lookup, but it does not explain the 'x-hapi-auth-state' parameter at all. The description adds little beyond what the parameter name already suggests.
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?
The description uses the specific verb 'Find' with the resource 'pet' and the scope 'by ID', clearly distinguishing this from sibling tools like findPetsByStatus or findPetsByTags. The phrase 'Returns a single pet' reinforces the tool's specific purpose.
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 description implies usage when you have a pet ID by saying 'by ID', but it does not explicitly state when to use this tool over alternatives or list any exclusions. For a full guidance it would need to mention, for example, that this tool is for fetching a specific pet rather than searching by status or tags.
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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