AWS MCP Server

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

Annotations provide strong behavioral hints (readOnlyHint: true, destructiveHint: false, etc.), so the bar is lower. The description adds minimal context by specifying 'all' instances and region scope, but doesn't disclose additional traits like pagination, rate limits, or authentication needs. It doesn't contradict annotations, but adds limited value beyond them.

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 that front-loads the core purpose without unnecessary words. Every part of the sentence earns its place by specifying the action, resource, and scope clearly.

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 low complexity (list operation) and rich annotations covering safety and behavior, the description is adequate but incomplete. It lacks output details (no output schema provided) and doesn't address potential nuances like error handling or result formatting, leaving gaps for an AI agent to infer.

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 'DBInstanceArgs' lacking detailed description. The description mentions 'region' and implies filtering via 'all instances', but doesn't explain the 'DBInstanceIdentifier' parameter's role in filtering beyond what the schema hints at. 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 ('List') and resource ('RDS DB instances') with scope ('in the given region'), making the purpose unambiguous. However, it doesn't explicitly differentiate from sibling tools like 'list-ec2-instances' or 'list-amis' beyond the resource type, which prevents a perfect score.

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 is provided on when to use this tool versus alternatives. The description doesn't mention sibling tools like 'list-ec2-instances' for other resources or clarify if this is the primary way to list RDS instances versus other methods. It lacks context about prerequisites or typical use cases.

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