cache_stats

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

Without annotations, the description states 'Read-only — no side effects' which is a clear behavioral trait. It doesn't cover error handling or response format, but for a read-only stats tool, this is adequate.

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?

Four short sentences, each providing distinct value: purpose, read-only nature, parameter source, and usage boundaries. No unnecessary words.

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 the simple tool (one parameter, read-only stats), the description covers purpose, parameter, usage guidance, and alternatives. It lists the stats returned, compensating for lack of output schema.

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 single parameter instance_id is adequately described in both schema and description. The description says 'identifies the target instance (obtain from list_instances)', which matches the schema description. With 100% schema coverage, the description adds little new meaning.

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 states it 'get real-time stats for a cache instance' listing specific metrics like memory usage, hit/miss rate, commands/sec, etc. It distinguishes from siblings like cache_get, cache_exists, and cache_ttl by explicitly saying it's not for reading cached values or key-level information.

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 says to use for monitoring, capacity planning, or debugging performance issues, and not for reading cached values (use cache_get) or key-level info (use cache_exists or cache_ttl). It also tells how to obtain the instance_id from list_instances.

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