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

Annotations already declare readOnly/idempotent/non-destructive, so safety needs no restating. The description adds value annotations can't: the 25-holding cap, the entitlement gate that will block non-broad sectors, and the non-obvious semantic that holding quadrants are measured against the sector ETF rather than SPY. Only the absence of any mention of latency or payload size keeps it below 5.

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 the purpose before the return detail and the tier rule. The holdings-field enumeration is dense but earns its place because there is no output schema; a tighter phrasing would drop the redundant '"quadrant against the sector ETF (not against SPY)"' restatement only slightly.

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 return-value burden and does so thoroughly: what top-level metrics appear, what each holding row contains, how many holdings max, and which symbols are gated. Combined with the one-parameter schema and read-only annotations, an agent has everything needed to call it correctly and interpret the result.

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% and the schema already gives examples (XLK, URA), so baseline is 3. The description earns an extra point by enumerating the 11 free tickers, which directly informs symbol choice and predicts whether a call will succeed or hit the paywall.

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 states a specific resource ("one sector ETF in depth") and enumerates exactly what comes back: quadrant, momentum, returns vs SPY, valuation, top holdings. "One ... in depth" implicitly contrasts with the sibling zensei_sectors_scan, which the description names as the symbol source. It does not differentiate against zensei_view_sector or zensei_stock_detail, which are the closest remaining siblings.

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 gives a concrete entry path ("Get symbols from zensei_sectors_scan") and an entitlement rule (11 named broad sectors are free, everything else needs Premium). It stops short of explicit "when not to use" guidance, e.g. whether zensei_view_sector is the lighter alternative to this deep-dive.

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