AWS MCP Server

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

No annotations are provided, so the description carries full disclosure burden. It explains the DryRun behavior for readonly mode but fails to mention critical behavioral aspects: that invocations incur costs, security implications of executing arbitrary code, sync vs async behavior differences, or what return values to expect.

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?

Two sentences with zero waste. The first sentence front-loads the primary purpose, and the second adds specific behavioral context about readonly mode. Every word earns its place.

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?

For a 5-parameter tool with side effects and no output schema, the description covers the basic invocation pattern but leaves significant gaps regarding cost implications, execution guarantees, error handling, and the shape of returned execution results.

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?

With 100% schema description coverage, the schema sufficiently documents all parameters. The description mentions 'InvocationType=DryRun' which adds context beyond the enum values (RequestResponse/Event) in the schema, but doesn't elaborate on payload format or profile selection criteria.

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 uses a specific verb ('Invoke') and resource ('Lambda function') that clearly distinguishes this tool from siblings like aws_lambda_get_function (metadata) and aws_lambda_list_functions (enumeration). The first sentence alone provides clear purpose.

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 mentions '--readonly mode' and explains it validates permissions without executing, which provides one usage context. However, it lacks explicit guidance on when to use RequestResponse vs Event, or when to prefer this tool over the generic aws_execute sibling.

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