Read PG stat IO

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

Annotations already declare readonly and non-open-world. Description adds version-dependent behavior (empty result on unsupported versions), revealing a critical edge case beyond annotations. No contradiction.

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?

Two sentences front-load the core purpose and then add essential version behavior. Every sentence adds value; no redundancy or fluff.

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?

Covers the main purpose, version dependency, and counters reported. With output schema present, return format is handled. Minor gap: no mention of pagination or large result sets, but acceptable for a read tool.

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% with clear description for the single optional parameter (database). Description does not add parameter-specific meaning beyond what the schema provides, so baseline score applies.

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?

Clearly states the tool reads the pg_stat_io view (PostgreSQL 16+), reports specific cumulative I/O counters, and is a read-only operation. The verb 'read' and resource 'pg_stat_io' are specific, making the purpose unambiguous.

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 context for use (spotting buffer-cache misses, write amplification) and explicitly mentions version dependency (returns available=false on PG 14/15). Lacks direct when-not or alternative tool references, but the guidance is clear.

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