List EC2 security groups in a specified AWS region and retrieve their group IDs for use when launching instances.
List EC2 security groups in the given region. Use the group_id values as entries in the security_group_ids list passed to aws_run_instances.
| Name | Required | Description | Default |
|---|---|---|---|
| region | Yes | AWS region (e.g. us-east-1). | |
| account | No | AWS account label to act in; omit for the default account. |
Changes observed during successful MCP inspections.
v2.28.0Input schema / properties / accountAdded value: +{
+ "description": "AWS account label to act in; omit for the default account.",
+ "type": "string"
+}v2.24.0v2.23.8v1.0.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full behavioral burden. 'List' implies a safe read, and it does disclose how the output feeds aws_run_instances, but it says nothing about pagination, permissions required, or result shape. Partial disclosure against a full burden yields a 3.
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 tight sentences, front-loaded with the purpose and followed by the actionable integration hint. Every sentence earns its place with zero filler.
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 two-parameter read-only list tool with no output schema, the description covers purpose, scope, and how to use the result, which is nearly all an agent needs. It omits only return/pagination details, a minor gap for a simple list operation.
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 coverage is 100%, so both region and account are already documented in the schema. The description only restates the region scoping ('in the given region') and adds no semantics for the optional account parameter, giving no value beyond the schema. Baseline 3 is correct.
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+resource+scope: 'List EC2 security groups in the given region.' The resource (security groups) is distinct from other aws_list_* siblings (amis, subnets, regions), so the agent can distinguish it without opening schemas. It stops short of explicit sibling differentiation, which keeps it at 4.
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?
Provides concrete downstream guidance: use the returned group_id values as entries in security_group_ids passed to aws_run_instances. This tells the agent why and when to call it (as a discovery step before launching instances). No when-not-to-use or exclusion conditions are given.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.