AWS MCP Server

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations provide destructiveHint=false, indicating it's non-destructive (creates new resources). The description adds that it launches instances, which aligns with annotations. However, it lacks behavioral context like cost implications, permissions needed (AWS IAM), rate limits, or that it may incur charges. With annotations covering safety, a 3 is appropriate—some value added but minimal behavioral disclosure.

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 a single, efficient sentence with zero waste—'Launch an EC2 instance in a given region'. It's front-loaded with the core action and resource, making it easy to parse. No extraneous information or redundancy is present.

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?

Given the complexity (2 parameters with nested objects, 50% schema coverage, no output schema, and no annotations beyond destructiveHint), the description is inadequate. It doesn't explain the return value (e.g., instance IDs), error conditions, or dependencies on other AWS resources. For a tool that creates infrastructure with many configurable options, more context is needed to guide effective use.

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 50%, meaning half the parameters lack descriptions in the schema. The tool description mentions 'region' and implies configuration via 'Ec2Args', but adds no semantic details beyond what's in the schema (e.g., explaining that 'Ec2Args' includes critical fields like 'ImageId' or 'InstanceType'). It doesn't compensate for the low coverage, leaving many parameters under-explained.

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 clearly states the action ('Launch') and resource ('EC2 instance') with the constraint 'in a given region'. It distinguishes from other EC2-related tools like 'start-ec2-instance' or 'terminate-ec2-instance' by specifying creation rather than state management. However, it doesn't explicitly differentiate from 'create-ami' or other creation tools in the sibling list.

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 provides no guidance on when to use this tool versus alternatives. It doesn't mention prerequisites (e.g., needing a VPC, subnet, or security group first), nor does it contrast with other instance management tools like 'list-ec2-instances' or 'reboot-ec2-instance'. The agent must infer usage from the name alone.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.