list_instances

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

Discloses read-only nature, return format (array of objects with specific fields), empty array if no instances, no pagination, and typical account size (<20), covering key behavioral traits beyond annotations (which are absent).

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?

Concise, front-loaded with main action, then read-only, return format, usage guidance—all in a few sentences with no 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?

Given no parameters and no output schema, the description fully covers the tool's behavior, return format, typical usage, and relationship to sibling tools, making it complete for its purpose.

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?

No parameters exist, so the description cannot add parameter semantics beyond the empty schema. Baseline 4 is appropriate for zero-parameter tools; description does not need to compensate.

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 it lists all cache instances with status and connection details, explicitly mentions read-only, and distinguishes itself from get_instance and other cache tools that require instance UUIDs.

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?

Provides explicit guidance: 'Use this first to discover instance UUIDs required by all other cache tools' and notes that get_instance retrieves full metadata for a single instance, giving clear when-to-use and alternatives.

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