TCGplayer market prices (BYO key)

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

Annotations already cover read-only and open-world behavior, so the description's 'Read-only' adds nothing. What does add value is the BYO-key authentication requirement and the disclosure of what is returned (five price tiers broken out by subtype), which the agent cannot learn from annotations alone.

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 terse clauses, front-loaded with the return payload, then the id constraint, then the prerequisite. Every fragment carries information; nothing is padding.

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 one-parameter read tool with no output schema, the description tells the agent what comes back and what credentials are needed. The remaining gap is discoverability of product ids and the absence of a response shape, but neither blocks 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 0%, so the description must carry the parameter meaning — and it does partially, clarifying that productIds are TCGplayer product ids and that the cap is 50 (the schema states maxItems but not what an id is or where to get one). It omits any pointer to a lookup tool, leaving a real gap for a zero-coverage schema.

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 concretely what the tool returns (market/low/mid/high/direct-low prices per Normal/Foil subtype) for a specific resource (TCGplayer product ids). The 'TCGplayer' qualifier implicitly separates it from cardmarket_price_guide and scryfall_card_prices, but it never names those alternatives 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?

Usage is implied by the marketplace name and the 'Requires your own TCGplayer keys' prerequisite, which is a useful gating condition. However, it never says when to prefer this over cardmarket_price_guide or scryfall_card_prices, nor how to obtain product ids (presumably via tcgplayer_product_search).

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