db_list_instances

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

No annotations are provided, so the description rightly carries behavioral disclosure: it states 'Requires AWS credentals' and implicitly signals a read-only list operation. It also hints at the return contents (endpoints, status). However, it doesn't mention default behavior when no filters are passed, pagination, or regional scope, leaving meaningful behavioral gaps.

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, each earning its place: the first defines action and resource, the second gives the credential requirement and intended use. It is front-loaded and free of redundancy.

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 simple list operation with optional filters and no output schema, the description covers the essentials: action, resource, credentials, intended use, and result hints. It could be more explicit about listing all instances when no filters are given and about response shape, but it is reasonably complete.

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?

Both parameters are fully described in the input schema ('Filter by database engine' and 'Filter by specific RDS instance identifier'), so schema coverage is 100%. The description itself adds no parameter-level detail, so a baseline 3 is appropriate.

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 ('List') and resource ('RDS database instances in the AWS account'), and its discovery intent distinguishes it from sibling tools that test connections, query, write, or inspect schema/tables. The opening sentence leaves no ambiguity about what the tool does.

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?

It explicitly instructs 'Use this to discover available databases, their endpoints, and status,' which gives a clear invocation context. It stops short of naming alternatives or saying when not to use it, but the discovery-vs-operation distinction is easy to infer from sibling names.

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