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

readOnlyHint=true already tells the agent this is a safe read, and the description is consistent with that by describing displayed rows rather than an action. It adds the meaningful 'out of combat' precondition and the returned fields, but says nothing about whether results vary by player state or what happens if no perks are available.

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?

One compact sentence that front-loads the resource and tucks the UI location and returned fields into a parenthetical. Every clause carries information, though the nested parenthetical and quotes make it slightly denser than necessary.

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, no output schema and read-only annotations, the description carries most of the burden and does explain the row shape (id, price, requirements) plus the out-of-combat restriction. The missing piece is the handoff to game_perk_buy for the actual transaction.

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 takes zero parameters, so there is no parameter meaning to add beyond the schema. Baseline 4 applies; the description's field list describes output rather than inputs and so neither helps nor harms here.

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?

States the specific resource (the perk-purchase window / vendor 'Perks' rows) and what it yields (id, price, requirements), which is far more informative than the name game_perk_shop alone. It does not explicitly name the sibling game_perk_buy as the action counterpart, so differentiation is implied rather than stated.

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 parenthetical '«Купить перки» в панели перков, вне боя' gives real context — open this when out of combat from the perk panel — which implies when to use it. However, it never states that this only lists the vendor and that game_perk_buy must be used to actually purchase, leaving the key alternative unspoken.

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