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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds rich behavioral context: demo-catalog behavior without owner auth, server clamping limit to 8, preferredStoreRoutingRu/catalogSearchScopeRu store routing, clarifyHint/quietHint semantics, basket/recipe behavior, and authentication via sessionId. It also discloses the data is 'not stale training data' and warns against memory quotes.

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 dense and front-loaded with the core purpose, but it is very long and covers many edge-case behaviors (clamping, routing, basket/recipe, sportpit preconditions, negative instructions). Every sentence earns its place, yet the sheer volume makes it harder to parse. It is structured as a block of rules rather than clearly separated sections, so a 3 is appropriate.

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 complex search tool with 8 parameters, no output schema, and 25 siblings, the description covers nearly everything an agent needs: when to call it, when not to, what the response includes, how to route based on preferredStoreRoutingRu, how to handle clarifyHint, sessionId passage, and prohibitions. The lack of an output schema is offset because the description enumerates the returned fields and their meaning.

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%, so the baseline is 3, but the description adds substantial value beyond the schema: it clarifies q/text aliases are product-only strings (not addresses), explains limit clamping without owner auth (do not retry), and details sessionId usage with begin_agent_link/connector scenarios. The description also tells the agent to prefer q over aliases and how to interpret the returned fields.

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 states a specific verb and resource: 'Search products in allowlisted AgentPay stores,' and differentiates itself from siblings by naming when NOT to use it (e.g., don't search for idioms like 'как обычно' — use list_purchases). It clearly identifies its scope (demo catalog vs owner's list) and return payload (ProductCard fields).

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?

Explicitly lists trigger phrases («актуальная цена», «есть в наличии», «сколько стоит», after «купи», «закажи», etc.), says when to call alternatives (get_product, list_purchases, peek_stores), and provides precondition logic (call begin_agent_link before a real buy, get_user_preferences for sportpit). It also gives exclusions: never web-search, never quote price from memory, never dump results.

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