AWS MCP Server

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

Annotations already indicate this is a non-destructive, idempotent write operation (readOnlyHint=false, destructiveHint=false, idempotentHint=true). The description adds minimal behavioral context beyond this—it doesn't explain what happens if the instance is already running, potential costs, or error conditions. However, it doesn't contradict the annotations.

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, clear sentence with no wasted words—it directly states the tool's purpose. It's appropriately front-loaded and efficient, making it easy to parse quickly.

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 tool's moderate complexity (starting cloud instances), annotations cover safety aspects, but the description lacks details on behavioral outcomes, error handling, or output format. With no output schema, the description should ideally hint at what's returned (e.g., success status or instance state), but it doesn't. It's minimally adequate but leaves gaps for an agent to infer usage.

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%, with the 'region' parameter well-documented but 'Ec2Args' object lacking internal descriptions. The description mentions 'in a given region', which aligns with the schema but doesn't add meaningful details about parameter usage, such as the format of InstanceIds or when to use DryRun. It partially compensates for the coverage gap but not fully.

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 ('Start') and resource ('an EC2 instance') with regional context ('in a given region'), making the purpose immediately understandable. It doesn't explicitly differentiate from sibling tools like 'launch-ec2-instance' or 'reboot-ec2-instance', but the verb 'Start' is specific enough for basic distinction.

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 like 'launch-ec2-instance' (for creating new instances) or 'reboot-ec2-instance' (for restarting running instances). It also doesn't mention prerequisites such as needing a stopped instance or appropriate AWS permissions.

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