market_session

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

On top of readOnlyHint/openWorldHint annotations, the description discloses that the tool is cached for only 5 seconds and explains why staleness matters. The 'PENDING VERIFICATION' note is an unusual but valuable disclosure about reliability.

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 carry distinct information: purpose, usage, cache behavior, and confidence status. The most decision-relevant fact (what session it is) is front-loaded, and there is no 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?

For a parameterless status tool with no output schema, the description provides the full set of possible return states, timezone/hours, and a caution about stale values. An agent has everything it needs to decide when and how to use this 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?

There are zero parameters and the schema already covers this fully; the description simply confirms 'Takes no arguments'. Per the baseline for no parameters, this is sufficient and adds no unnecessary detail.

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 leads with a precise statement of what the tool reports — the current IDX trading session among six enumerated states — and names the resource ('the IDX trading day'). This is specific enough to distinguish it from generic 'status' or 'trading_status' siblings, even without naming them.

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 explicitly instructs when to call it ('BEFORE concluding that an empty movers list, a still order queue or a silent tape means something is broken') and gives operational context about WIB hours and holidays. It also warns about the 5-second cache, which tells the agent to re-call it frequently.

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