AWS MCP Server

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

No annotations provided, so description carries full burden. It successfully discloses the exhaustive nature ('reads every item') and cost implications ('use sparingly'), but lacks critical operational details like pagination behavior (NextToken/LastEvaluatedKey), consistency model, or read capacity consumption that agents need for safe invocation.

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?

Three sentences, zero waste. Front-loaded with the action ('Scan a DynamoDB table'), followed by critical warnings and alternative guidance. Every clause earns its place in guiding agent selection.

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 7 parameters with nested objects and no output schema, the description adequately covers the primary selection criteria (operation type, cost warnings, and query alternative). However, it lacks return value documentation and pagination semantics which would be necessary for complete operational understanding.

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 100%, establishing a baseline of 3. The description does not add parameter-specific semantics, examples, or syntax guidance beyond what the schema already provides for the complex expression attributes and DynamoDB format objects.

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?

Excellent specificity: 'Scan' is the exact API operation, 'DynamoDB table' identifies the resource, and '(reads every item)' clarifies the exhaustive scope. Critically, it distinguishes from the sibling aws_dynamodb_query tool by stating when to prefer that alternative.

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 explicit guidance: 'Use sparingly on large tables' warns against expensive operations, and 'Prefer query when you know the partition key' directly names the alternative tool and condition for using it. Covers both when-not-to-use and alternatives.

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