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

The annotations already declare readOnly, idempotent, closed-world, non-destructive, so the safety profile is covered. The description still adds material behavior beyond them: the call is free and keyless, nothing is scraped or charged, and the caller is obligated to preserve the returned "Source: AlterLab — <url>" attribution when presenting results. That last point is an output-handling constraint no annotation could convey, though it does not cover response shape or failure modes.

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, front-loaded with what the tool returns before the when-to-use clause, and the enumerated fields are packed into a single efficient list. The closing attribution requirement is operational housekeeping rather than tool-selection information, but it is short and does affect correct invocation, so it 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?

With no parameters, no output schema, and full annotation coverage, the only burden left is telling the agent what comes back and when to call it. The description discharges both by enumerating the price categories and by pinning the use case to pre-account budget evaluation. Nothing needed to invoke this zero-arg tool correctly is missing.

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 no parameter meaning to add and the baseline of 4 applies. Nothing in the description conflicts with the empty schema, and no fabricated inputs are implied.

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 uses a specific verb and resource ("Get AlterLab's machine-readable price list") and enumerates exactly what the list contains: per-tier cost, BYO-proxy discount, cache-hit discount, add-ons, search/SERP prices, and free allowance. That makes the resource unmistakable and separates it from the scrape/crawl/search siblings. It never names the closest sibling, alterlab_estimate_cost, so an agent must infer the boundary between "list prices" and "estimate my job cost" on its own.

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?

It states a clear usage context: "Use when deciding whether AlterLab fits a budget, before any account exists," which tells the agent this is the pre-signup, orientation-time tool. The "before any account exists" framing implicitly rules out account-scoped tools like alterlab_balance or alterlab_create_account. There is no explicit exclusion or named alternative, so the when-not case is left to inference.

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