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

Annotations already declare readOnlyHint, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely useful behavior beyond that: it states the null-on-unknown-ticker contract, defines units (IDR per share, shares vs IDR), and discloses which fields are computed (changePercent, foreignNet).

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 purpose is front-loaded in sentence one, and the rest is a dense but organized glossary of profile keys, units and computed fields. It is long, but the length is largely earned because no output schema exists to carry the return contract.

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 output schema, the description must carry the return contract, and it does: it enumerates the profile sections, maps IDX key names to meanings, specifies units and currencies, defines derived fields, and documents the null case. An agent can interpret the response without any other source.

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 description coverage is 100% and the single 'code' parameter already documents the ticker format and gives the BBCA example. The description adds no syntax or format detail beyond the schema, so the baseline 3 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?

The first sentence gives a specific verb ('Fetch'), resource ('IDX-listed company'), and access key ('by ticker'), then enumerates the returned sections, which implicitly separates it from the lighter search/list siblings. It never names a sibling explicitly, so it stops short of a 5.

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?

Usage is implied: use this when you already have a ticker and want the full profile. There is no explicit when-to-use/when-not statement and no routing to Idx_search_companies for discovery or Idx_price_history for series data.

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