List EC2 instances in a specified AWS region to view running and stopped resources.
[SAFE] List EC2 instances
This tool declares no required parameters. Add optional parameters from the input schema as needed.
{
"id": 1,
"jsonrpc": "2.0",
"method": "tools/call",
"params": {
"arguments": {},
"name": "aws_ec2_instances"
}
}| Name | Required | Description | Default |
|---|---|---|---|
| region | No |
Changes observed during successful MCP inspections.
v1.0.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The '[SAFE]' tag hints at read-only behavior, but there is no disclosure of pagination, error handling, or output format. Given no annotations, the description fails to provide sufficient behavioral transparency.
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 extremely concise (one line), but it sacrifices necessary detail. While front-loading with '[SAFE]' is good, the brevity leads to gaps.
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?
Without an output schema, the description should explain return values. It does not. For a listing tool, details on response format or filters are missing, making it incomplete.
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?
The 'region' parameter is not described in the description. With 0% schema description coverage, the agent receives no guidance on its meaning or usage.
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 'List EC2 instances' clearly states the action (list) and resource (EC2 instances), distinguishing it from sibling tools like aws_lambda_functions. However, it lacks specificity about scope (e.g., region or account).
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 guidance on when to use this tool vs alternatives, nor any prerequisites or context. The description is too brief to inform decision-making.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.