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

With no annotations, the description carries the full burden and does so: it discloses the frozen-input state and required phrasing ('Say last published, never today'), the usd_panel {frozen, as_of} marker, that the call is free with no payment required, that horizon is fixed at 30 days, and that momentum grade can be 'NA' on a drift spike. This is far beyond what a typical definition offers.

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?

The frozen-input caveat is correctly front-loaded because it changes how any agent should phrase its answer, then the core one-card summary, then usage, then escalation. The returned-field list is long but earns its place since no output schema exists. Slightly verbose overall, but no sentence is pure filler.

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?

Given no output schema and no annotations, the description supplies the return-object field list, the frozen-data caveat, cost model, horizon constraint, escalation path, and a sample plain_english read. An agent has everything needed to call it and to interpret the response.

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 compensate, and it does partially: card_name is 'resolved to the best match' (fuzzy resolution semantics) and product_id is a 'TCGplayer product_id' (namespace semantics). It does not explain that both are optional with default empty/zero values or how the two are prioritized when both are supplied.

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 deliverable on a specific resource: 'The FREE 30-day read on ONE card: point forecast, bands, VaR, and the Safe-Hold / Momentum letter grades, in one call.' It immediately distinguishes itself from simulate_price by naming the horizon (fixed 30 days) and the exact outputs, so an agent can tell it apart from sibling forecasting tools.

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?

Explicit routing: 'Use this FIRST for is this card a safe hold?, 30-day outlook?, how risky is X?' followed by when-not and the alternative — 'For other horizons, the full percentile curve, or Monte Carlo paths, escalate to simulate_price (paid).' It also points to a free market-overview endpoint for a different intent.

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