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

With no annotations, the description carries the full burden. It does disclose the substance of what comes back — duty-cycle assumptions, which rental sources, break-even analysis, posted GPU-hour prices, and HF download counts — which is useful content transparency. However, it says nothing about behavior: whether these are static snapshots or live figures, data currency, or result format, all of which matter for a zero-annotation tool.

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, no filler, and the core value (cost per 1M tokens to leave the APIs) is front-loaded. The second sentence ('Plus posted GPU-hour prices...') reads as a tacked-on appendix and the first sentence is a dense run-on, which keeps it below a 5.

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 parameters and no output schema, the description must convey what the caller receives, and it enumerates the report's contents (per-source hardware costs, break-even, GPU-hour prices, download counts) in enough detail to set expectations. Missing freshness/format information is a modest gap given the tool's static-analysis nature.

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; baseline 4 applies. The description correctly does not waste space describing an empty 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?

The description makes clear this tool returns a self-hosting economics comparison: per-1M-token cost of local/rented/owned hardware versus API pricing of open and closed models. It names the resource (hardware vs API cost) precisely, but the bare name 'self_hosting' and the absence of any named sibling keep it short of a 5. It does not explicitly differentiate from model_price or open_vs_closed, which cover adjacent pricing territory.

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?

The description implies the use case (deciding whether to leave APIs for hardware, needing break-even volume), but it never states when to call this instead of model_price, open_vs_closed, or cost_per_task. No exclusions, prerequisites, or routing guidance are given, so usage is inferred rather than instructed.

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