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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds genuinely new behavior: the payload shape and the host-dependent card rendering under MCP Apps. It does not discuss localization fallback behavior for the language enum, which is the one remaining trait an agent might want.

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?

Two sentences, zero waste, with the identifier requirement and provenance front-loaded before the conditional rendering note and the usage trigger.

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?

Output schema exists, yet the description still previews the returned fields and explains host-dependent rendering, so an agent knows both when to call it and what to expect. Nothing needed for correct invocation is missing.

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 both parameters are already documented, including the productId provenance and the language enum. The description only reinforces where productId comes from and says nothing about the language parameter, so it adds marginal value over the schema — baseline 3.

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?

Names a specific verb and resource ("Show full details for a single product/menu item by product_id") and enumerates exactly what comes back (image, description, price/discount, stock, addons). That scope cleanly separates it from siblings like search_merchant_products or get_full_menu.

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 states the trigger ("when the user taps a product or asks about a specific item") and routes the agent to search_merchant_products as the source of the id. No explicit when-not or exclusion against siblings, which keeps it short of a 5.

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