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

Annotations already declare readOnly, openWorld and non-destructive, so the safety profile is covered. The description adds genuinely non-obvious behavior: the data is public and cached, no API key is needed, and several algorithms return null because no primary MRR book exists. That null-value disclosure is exactly the kind of context an agent cannot get from the schema or annotations.

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 endpoint and resource lead the sentence, followed by the operational facts that matter. The enumeration of SHA3X, zkSNARK, Blake256R14, Kadena and XPHash is dense but earns its place because it explains which results will be null.

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?

With no output schema, the description carries the burden of explaining return semantics, and it does address the most misleading case (null rates for algorithms without an MRR book) plus the NexaPow aliasing. It stops short of describing the shape of a rate entry, which would fully close the gap for a listing tool.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate and the baseline is 4. The schema is an empty object and the description correctly does not invent parameter guidance.

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 names a specific endpoint and resource ('GET /api/v1/mrr-rates — public cached Mining Rig Rentals algorithm rates'), which is clearly distinct from sibling tools like list_nicehash_rates or get_market. It does not explicitly name the sibling that covers NiceHash rates, so differentiation relies on the 'MRR' qualifier rather than a direct contrast.

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?

'Market snapshot, not a rental booking' implies a when-not boundary, and 'No API key required' removes a precondition concern. However, it never states when to prefer this over list_nicehash_rates or calculate_profitability, leaving the agent to infer the choice from the resource name.

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