AWS MCP Server

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

Annotations already provide readOnlyHint=true, destructiveHint=false, openWorldHint=true, and idempotentHint=true, covering safety and idempotency. The description adds the regional scope constraint ('in the given region'), which is useful context beyond annotations. However, it doesn't disclose other behavioral traits like pagination details (implied by ContinuationToken in schema) or rate limits, keeping it at a moderate score.

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 zero wasted words. It's front-loaded with the core action and resource, making it highly efficient and easy to parse for an AI agent.

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 (2 parameters with nested objects), rich annotations (covering safety and idempotency), but no output schema, the description is minimally adequate. It states what the tool does but lacks details on output format, error handling, or usage context, leaving gaps that could hinder an agent's effectiveness.

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 in the schema but 'S3Args' having nested properties described. The description mentions 'given region' but doesn't add meaning beyond what the schema provides for parameters like MaxBuckets or Prefix. It partially compensates for the coverage gap by implying regional filtering, but not enough to elevate the score.

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 verb ('List') and resource ('all the S3 buckets'), making the purpose unambiguous. However, it doesn't explicitly differentiate from sibling tools like 'list-amis' or 'list-db-instances' beyond mentioning S3 buckets specifically, which is why it doesn't reach a perfect 5.

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 mentions a region parameter but doesn't explain when to use this tool over other listing tools (e.g., for S3-specific operations vs. general AWS resource listing) or any prerequisites. This leaves the agent with minimal contextual direction.

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