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

Annotations already declare readOnly, idempotent, closed-world, non-destructive, so the safety profile is covered. The description adds genuinely useful context by saying unpublished numbers come with an explanation of why, and that the lead sentence is sourced from the fund's trading page — but it says nothing about format, staleness, or how missing data is signaled in the response.

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 lead clause 'What it costs to trade one ETF' is well front-loaded, but the rest is a single dense run-on packing four separate metrics plus a sourcing note. Splitting into 'returns X, Y, Z' plus a separate provenance sentence would be far easier to scan.

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 the return-value burden. It does enumerate the metrics, but phrases like 'ETFIQ's own premium from NAV and closing prices with its window' and 'IQ Liquidity Score on a fixed 0 to 100 scale' are jargon-dense and leave the shape of the response (fields, units, how 'why not published' is conveyed) ambiguous.

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?

There is only one parameter, ticker, and schema coverage is 100% with an example ('JEPI') already given. The description adds no constraint, format, or validation detail beyond the schema, so baseline 3 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?

The description makes the subject clear — cost-of-trading metrics (liquidity score, spread, premium/discount to NAV) for a single ETF — but it is phrased as a list of data fields rather than a verb+resource statement. It never distinguishes this tool from nearby siblings like etf_profile, etf_scorecard, or etf_compare, which likely also expose some of these fields.

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?

There is no guidance on when to call this versus the many other per-ETF tools in the sibling list, and no mention of prerequisites. An agent must infer usage purely from the field inventory.

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