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

Annotations already declare readOnly/idempotent/non-destructive, so safety is covered. The description adds genuinely non-obvious behavior: free tier returns counts, ranges and redacted samples while PRO returns vendor/model names and exact prices, and tokens are priced per 1,000 tokens while other modalities use their own units. That is real value beyond the 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?

Three sentences, front-loaded with what the tool returns and then the tier/unit rules. The pricing parenthetical and URL are mildly promotional but do convey the gating condition an agent must know, so they largely earn their 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?

No output schema exists, so the description must carry return-value semantics, and it does: counts/ranges/redacted samples vs vendor names and exact prices, plus unit definitions. The one gap is that it does not clarify the shape of the distributions (percentiles vs min/max), but for a relatively simple two-parameter tool this is close to sufficient.

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%, so modality and _atom_api_key are already documented, making 3 the baseline. The description goes further by explaining the unit convention that governs the numbers returned for each modality (per image, per second, per 1,000 characters), which the schema does not convey.

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 resource ('tracked market') and enumerates what it covers (vendors by channel, countries, models, priced SKUs, indexes) plus price distributions by modality/unit/direction. That is far more specific than a tautology, but it never names a sibling tool, so it does not explicitly differentiate itself from compare_prices or get_kpis.

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 implies the tool is the aggregate market-overview endpoint ('coverage of the tracked market'), and it usefully explains the free vs PRO tier condition. However, it never says when to pick this over get_kpis, get_vendor_catalog or compare_prices, so routing guidance is implicit rather than stated.

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