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

Annotations already declare readOnly and idempotent, so safety is covered. Description adds that data comes from a server-cached aggregate source with source and timestamps, and emphasizes it's a current snapshot, which informs the agent about data freshness and potential lag. No contradictions.

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?

Two sentences with no filler. Front-loads the core data content, then adds usage guidance. Every sentence earns its place.

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 no-parameter snapshot tool, the description covers what data is returned (market cap structure, dominance, stablecoin share), notes source/timestamps, and clarifies non-historical nature. Without an output schema, it provides enough context for an agent to understand the result, though it could be more specific about exact output format. Still complete for typical use.

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?

No parameters exist, so schema coverage is complete. The description doesn't need to explain parameters; baseline 4 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 purpose: reports current crypto market-cap structure including BTC/ETH dominance, total cap/volume, stablecoin share, and leading asset shares. Clearly distinguishes from historical backtest series, and mentions it's a current snapshot. This differentiates it from backtest_run and other historical 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?

Explicitly advises using this tool for BTC.D/rotation context, giving a clear when-to-use. Also clarifies it's not a historical series, implying not for backtesting. Does not name specific sibling tools but provides sufficient guidance.

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