list_instances

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

With no annotations, the description carries full burden for behavioral disclosure. It confirms the operation is read-only (list) and adds a critical safety note: 'Passwords are never included.' This addresses a key security concern beyond the schema.

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 two sentences: the first states the purpose, the second details output format and an important security guarantee. It is front-loaded, concise, and every sentence adds value.

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?

While the description covers the basic purpose and a security aspect, it does not clarify what constitutes a 'database instance' versus a 'database' (sibling list_databases exists). It also omits any mention of pagination, ordering, or performance implications, though the tool is simple with no parameters.

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?

The tool has zero parameters, and schema coverage is 100% (trivially). Per the rubric, 0 parameters yields a baseline of 4. No additional parameter info is needed or provided.

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 'List all registered database instances,' specifying the exact resource and action. It distinguishes from sibling tools like list_databases, list_tables, and register_instance by focusing on 'instances' rather than databases or tables.

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. It lacks explicit when-to-use, when-not-to-use, or alternative tool references, leaving the agent to infer context solely from the name and sibling list.

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