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

Annotations already cover read-only, idempotent and closed-world behavior, so the bar is lower; the description still adds a material trait not in the annotations — a paid call at $0.005 USDC via x402, which affects whether an agent should call it casually. It also discloses the output fields and that volatility can be 'unknown', but says nothing about failure modes for an unsupported asset.

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?

One compact block, front-loaded with the purpose and output fields, followed by usage, pricing, and discovery in a sensible order. The field enumeration is slightly dense but each clause (cost, discovery pointer) earns its place; no filler sentences.

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?

There is no output schema, so the description carries the return-value burden and does so by naming the exact fields returned (trend, volatility, SMA50 slope, 30-day volatility, close, dates) plus the enum values for trend and volatility. Combined with pricing, asset-discovery guidance, and the single fully-documented parameter, an agent has everything needed to call it correctly.

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% and the single 'asset' parameter is already documented in the schema with examples (BTC, ETH, SOL, regime-btc) and the list_assets pointer. The description only reinforces the one-asset scope and repeats the list_assets discovery hint, adding no new meaning beyond the structured fields — baseline 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 and resource ('Get the market regime for one crypto asset') and enumerates what the regime consists of: trend, volatility, SMA50 slope, 30-day volatility, close and dates. It distinguishes itself from get_signal by framing itself as a classification rather than a trade signal, but it does not differentiate itself from the sibling get_trend, which an agent could easily confuse with the 'trend' component described here.

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 says when to use it ('when you need a regime/volatility classification rather than a trade signal'), naming get_signal as the alternative, and routes asset discovery to list_assets. The gap is that get_trend is never mentioned as an alternative or exclusion, leaving one obvious sibling-routing decision unaddressed.

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