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

Annotations already declare readOnlyHint=false, destructiveHint=true and idempotentHint=false, but the description earns credit by spelling out the practical consequence of non-idempotency ('a repeat applies the change again') rather than just tagging it. It does not disclose whether the resulting level may go negative, what auth/permissions are needed, or what happens on a missing product/store.

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?

Three short sentences with the write nature signalled first, the core semantics second, and the idempotency caveat third. No filler, no repetition of schema content beyond what the sign convention needs.

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 4-parameter mutation with a fully described schema and no output schema, the definition covers purpose, sign semantics, and non-idempotency, which is enough to invoke it correctly. It stops short of failure modes and permission requirements, which matters slightly more given destructiveHint=true.

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 every parameter is already documented, including the sign convention for stock_amount ('+5 adds five, -3 removes three'). The description restates that same sign convention but adds nothing about store_id/product_id pairing or the memo field, so the baseline of 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?

States a specific verb pattern ('add (positive) or subtract (negative) a quantity') plus the resource and scope ('one product in one store'), which clearly separates it from an absolute setter. It never names smaregi_set_stock or smaregi_list_stock, leaving sibling differentiation to inference from the delta semantics.

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?

Implicit usage only: the agent learns this is a relative adjustment rather than an overwrite, which suggests preferring smaregi_set_stock for absolute values. No explicit when-to-use, when-not-to-use, or named alternative is provided, and nothing is said about preconditions such as the product/store existing or needing stock records.

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