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

With no annotations, the description carries the full burden. It discloses the meaningful constraint that points only work on house goods, which is genuinely useful, but it omits whether purchases are reversible, whether credits are deducted immediately, and auth/balance requirements for a mutation tool.

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?

A single sentence, front-loaded with the verb and payment modes, with zero filler. It is appropriately sized, though the parenthetical could be slightly clearer about the conditional.

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 purchase mutation with no annotations and no output schema, the description covers the payment-mode nuance but omits auth, balance precondition, and post-purchase effects, leaving gaps an agent would need to infer.

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 60%, so baseline is 3. The description adds real meaning to pay_with by restricting 'points' to house goods, but leaves qty and input unexplained beyond their terse schema entries.

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+resource ('Buy a market item') and clarifies the two payment modes, including that points apply only to house goods. It implicitly separates itself from siblings like list_market or house_get, but never names an alternative explicitly.

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 description implies when points may be used ('on house goods') but gives no explicit when-to-use vs alternatives and no prerequisite statement (e.g., auth, sufficient balance, or that the item must be listed).

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