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

Annotations already declare destructiveHint=true, idempotentHint=false and openWorldHint=true, so the safety profile is covered. The description adds real behavioral context beyond that: the 'at least one field must be provided' precondition, that prices are absolute levels rather than deltas, and the broker-specific restriction that Binance requires cancel-and-replace. It does not state what the call returns or whether the order ID is preserved.

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?

Four sentences, each doing distinct work: what it is, what you can change, the validation constraint, and the broker exception. Front-loaded with the core action and free of filler.

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?

For a 6-parameter mutation tool with full schema coverage and annotations that carry the safety profile, the definition supplies preconditions, price semantics, and the key broker exception. The only gap is the absence of any statement about the outcome of a successful modification (e.g., new order ID, whether the order is re-queued), with no output schema to compensate.

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 description coverage is 100%, so the baseline is 3. The description earns above baseline by clarifying that price values are absolute levels (not offsets or percentages), a semantic distinction the schema descriptions ('New entry price', 'New stop loss price level') do not make explicit.

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 verb and resource ('Modify a pending order') and immediately disambiguates scope by defining a pending order as a limit/stop order waiting to be filled, separating it from modify_position. It also enumerates the mutable fields, so an agent knows exactly what this tool covers.

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?

Gives explicit trigger scenarios ('move a limit order to a different price, change lot size, or adjust SL/TP on a pending order') and names a concrete alternative path for a broker that does not support it, routing to cancel_broker_order plus a new order. This is textbook when-to-use and when-not-to-use guidance.

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