AWS MCP Server

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

Annotations indicate this is a non-destructive, idempotent, open-world write operation (readOnlyHint: false, destructiveHint: false, idempotentHint: true, openWorldHint: true). The description adds no behavioral details beyond 'Create', such as what happens on conflicts, rate limits, or authentication needs. It doesn't contradict annotations but provides minimal extra context, meeting the lower bar with annotations present.

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, direct sentence with zero wasted words, front-loading the core action and resource. It's appropriately sized for a tool with annotations and a detailed schema, avoiding redundancy while stating the essential purpose efficiently.

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 complexity (2 parameters with nested objects, 50% schema coverage, no output schema) and annotations covering safety but not operational details, the description is inadequate. It doesn't explain critical aspects like required VPC association, idempotent behavior, or what the tool returns, leaving significant gaps for a mutation tool in a cloud environment.

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 detailed descriptions for nested SubnetArgs properties but none for the top-level 'region' parameter. The description mentions 'region' but adds no semantic context beyond what the schema implies (e.g., AWS-specific usage). It doesn't compensate for the coverage gap or clarify parameter interactions, aligning with the baseline for moderate schema coverage.

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 ('Create') and resource ('a subnet'), and specifies the context ('in the given region'), making the purpose immediately understandable. However, it doesn't differentiate this tool from other subnet-related tools like 'create-vpc' or 'update-subnet-attribute' beyond the basic verb, missing explicit sibling 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 'create-vpc' for broader network setup or 'update-subnet-attribute' for modifications. It lacks any mention of prerequisites (e.g., needing an existing VPC), exclusions, or recommended workflows, offering minimal contextual direction.

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