list_instances

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

Discloses read-only nature, return structure (list of objects with specific fields), empty array if none, and all-at-once retrieval (no pagination). No annotations provided, so description fully carries the burden.

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 and well-structured: front-loaded with purpose, each sentence adds important information without 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 purpose, usage, return format, and edge cases. It is complete for the tool's simplicity.

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?

Input schema has no parameters (100% coverage). The description adds value by detailing the return structure and fields, which is not in the schema. Baseline 4 is appropriate with zero parameters.

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 verb 'list' and the resource 'cache instances' with scope 'all'. It distinguishes from sibling tool 'get_instance' by noting that this tool returns all instances and is used to discover 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?

Explicitly states 'Use this first to discover instance UUIDs required by get_instance, cache_get, cache_set, and all other cache tools.' It also mentions no pagination and typical account size, guiding the agent on when to use this tool.

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