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

Annotations only declare mutation/idempotency flags; the description supplies the critical behavior the agent cannot infer elsewhere — whole-set replacement where omitted fields revert to defaults, an api:account auth requirement, and a response echo. It also preempts a dangerous misreading by stating trade_routing 'never routes or places an order.'

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?

Front-loaded with the highest-stakes facts (replace-not-merge, fetch-then-resend) before the dense per-field reference. The long parenthetical enumerations are information-dense rather than filler, though the block is heavier than strictly necessary for an agent that can read the schema.

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, and the description covers the return behavior ('The response echoes what was stored'). Combined with the replace semantics, auth scope, per-kind field expectations, and the out-of-scope profile note, an agent has everything needed to call this correctly.

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?

With 67% schema coverage across nested objects, the description compensates well: it names the hidden_rows categories (global | crypto | fx | commodities | sectors | bonds), the 3-12 and ≤64 limits, the opportunity_hidden_subjects 'asset:…' id shape, and the ≤200 US-ticker constraint on symbol_overrides. Some of this restates schema enums, but it adds meaning (e.g., what symbol_overrides actually preselects) rather than just echoing.

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 opens with a specific verb+resource+ownership scope ('Replace one of YOUR preference sets (requires api:account)') and immediately disambiguates the two variants via kind. It clearly distinguishes itself from the sibling get_preferences, which it explicitly tells the agent to call first.

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 an explicit workflow (call get_preferences with the same kind, change only what the user asked for, send the whole set back) and names the sibling to use. It also gives a hard exclusion: 'The trading profile (risk caps, agent mode, chat execution) cannot be changed here.' Both when-to-use and when-not are covered.

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