AWS MCP Server

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

Annotations indicate this is a non-readOnly, non-idempotent, non-destructive operation (write operation that creates tags). The description doesn't contradict these annotations, but adds minimal behavioral context beyond them. It doesn't explain what 'create' entails (e.g., overwriting existing tags, error behavior, AWS API specifics), though annotations cover the basic safety profile. No additional context about rate limits, authentication needs, or side effects is provided.

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 maximally concise with just two words. While this represents severe under-specification rather than ideal conciseness, according to scoring rules, it receives full points for having zero wasted words and being front-loaded. Every word (both of them) directly states the tool's action.

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 mutation tool with 2 parameters (one complex nested object), 50% schema coverage, no output schema, and multiple sibling tools, this description is severely incomplete. It doesn't explain what the tool returns, error conditions, AWS-specific behaviors, or how it fits within the broader tagging workflow. The annotations provide basic hints but don't compensate for the description's inadequacy.

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% (region parameter is described, but InstanceArgs object and its nested properties lack descriptions beyond property names). The description provides no parameter information whatsoever - it doesn't mention required inputs like Resources array or Tags structure. With low schema coverage and no compensation in the description, parameters remain poorly documented.

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 'Create instance tag' is a tautology that merely restates the tool name without adding meaningful context. It doesn't specify what an 'instance tag' is (AWS EC2 instance tag), what resource it applies to, or how it differs from sibling tools like 'list-instance-tags' or 'delete-instance-tag'. The purpose is minimally stated but lacks differentiation and specificity.

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 zero guidance on when to use this tool versus alternatives. It doesn't mention prerequisites (e.g., needing an existing EC2 instance), when not to use it, or how it relates to sibling tools like 'list-instance-tags' (for viewing) or 'delete-instance-tag' (for removal). There's no contextual framing for this AWS tagging operation.

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