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

Annotations already declare readOnly/idempotent/non-destructive/openWorld=false, so the safety profile is covered. The description adds real behavioral context beyond that: results are net of fees and slippage and are size-dependent ('at your size'), and the output includes a tier and reasons, which signals non-actionable candidates may also be surfaced. It stops short of explaining what 'tier' or 'reasons' mean or how ranking works.

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?

A single dense sentence, front-loaded with the trade structures covered and closing with a colon-introduced list of returned metrics, so there is no filler. The run-on construction ('and two same-day futures on different exchanges') is slightly hard to parse and no verb anchors the sentence.

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 usefully enumerates the returned fields, which is the main gap it needed to fill. But for a five-parameter tool with 60% schema coverage it leaves actionable_only and limit unexplained and does not say whether results are sorted or ranked, so an agent cannot fully predict what it will get back.

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 60%; base, scope, and notional are documented in the schema, and 'at your size' in the description reinforces notional as position size per side. However, actionable_only carries no description in either the schema or the description, and limit is undocumented in both — so the description does not compensate for the coverage gap. Baseline 3 is appropriate.

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 specifies the resource precisely: spot/perp vs a dated future held to delivery, including cross-venue and same-day-futures variants, and lists the metrics returned (net to expiry, net APR, basis APR, max size, tier). An agent can tell this is a basis/term-structure screener rather than a generic rates tool. It does not, however, explicitly distinguish itself from near-siblings like boros_futures_basis or term_structure.

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 explicit when-to-use, when-not-to-use, or named alternative, despite the sibling list containing boros_futures_basis, fixed_vs_floating, and term_structure that could plausibly overlap. The 'held to delivery' phrasing implies a hold-to-expiry use case, but the agent must infer that from what is essentially a scope-of-coverage sentence rather than guidance.

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