Market indices

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

Annotations already signal read-only (readOnlyHint=true) and deterministic (openWorldHint=false), but the description adds significant behavioral context: the sign conventions (change and change_percent are signed, direction is up/down/flat derived from PSE Edge's color/arrow), the caching policy (at most once per boundary window), and the meta.as_of field for snapshot timing. This substantially goes beyond the annotations, delivering high transparency.

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?

The description is moderately sized (4 sentences) and front-loaded with the main purpose. Each subsequent sentence adds necessary detail (coverage, sign semantics, caching) without fluff. It could be slightly more compact, but it remains efficient and relevant, earning a 4 rather than a 5.

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?

With no parameters and an output schema present, the description covers all essential contextual aspects: what data is returned, which indices are included, the interpretation of direction fields, and the staleness/caching behavior. The existence of an output schema handles return field details, so the description is complete for an agent to select and invoke the tool correctly.

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 tool has zero parameters, and the schema coverage is 100% (vacuously). The baseline for zero-parameter tools is 4 per the rubric. The description adds no parameter info (not needed), so the score reflects the absence of complexity.

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 retrieves PSEi and PSE sector index levels with daily change. The verb 'Get' and specific resource 'PSEi and sector index levels' is explicit, and it naturally distinguishes from siblings like get_stock_quote (single stock) and get_market_summary (broader market metrics).

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?

The description clearly indicates the scope (which indices are covered) and the context (cached until 15:00 Manila close), which helps decide when to use it. However, it does not explicitly mention when not to use it or suggest alternatives, so it falls short of a 'when/when-not' distinction. Still, the clarity of purpose provides strong implicit guidance.

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