cache_exists

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

Discloses read-only, no side effects, return count of existing keys, duplicate keys counted separately. No annotations but fully covers behavioral traits.

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?

Single paragraph but well-structured with multiple sentences; no wasted words, though could be broken into bullet points for readability.

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?

No output schema or annotations, but description explains return value and behavior adequately. Lacks explicit mention of performance or that it requires a running instance (implied).

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 coverage is 100% so baseline is 3. Description adds context: instance_id from list_instances, keys accept exact keys only (no glob patterns), adding value beyond schema.

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 tool checks key existence in a cache instance, uses Redis EXISTS, and distinguishes from siblings like cache_get and cache_ttl.

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?

Describes when to use (before cache_get to avoid null handling, verify warmup) and when to use alternatives (cache_get for values, cache_ttl for expiry), but no explicit when-not.

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