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

With no annotations provided, the description discloses key behaviors: estimates are from recent sales, excludes fees/taxes/shipping, and disclaims as not financial advice. It also restricts to trading cards. Does not cover rate limits or error handling, but the disclosed traits are relevant and sufficient for an agent.

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?

Four sentences; front-loaded with purpose and outputs. Each sentence adds necessary detail. Minor redundancy in saying 'not financial advice', but overall efficient without unnecessary verbiage.

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?

No output schema, but the description lists all output components. Input options are well explained. Limitations (trading cards only, excludes fees) are stated. For a non-destructive query tool, the description is sufficiently complete to guide correct invocation.

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% with descriptions for both parameters. The description adds value by clarifying the mutually exclusive nature of query vs item, and enumerating the fields expected in the structured item object, which goes beyond the schema description alone.

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 specifies a clear verb ('Return a canonical market summary') and resource ('for a trading card'), listing specific outputs and domain. It effectively distinguishes from siblings like search_card_sales and get_card_price_history by focusing on synthesized market summary rather than raw sales or price history.

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 when to use: when user asks 'what's it worth', 'market value', or 'how volatile'. Provides domain constraint ('Trading cards only'). Does not mention when not to use or compare with sibling tools, but the guidance is clear and actionable.

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