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

Annotations already declare this is a non-readonly, non-destructive, closed-world mutation, so the safety profile is covered. The description adds the carrier-route prerequisite and clarifies marginType naming, but says nothing about what happens if a rate already exists on the route, whether values are overwritten, or what the response confirms.

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 short sentences, front-loaded with the action and scope constraint, then prerequisites, then the one tricky parameter. No filler or repetition.

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?

This is an eight-parameter mutation with no output schema and no annotation detail about side effects, yet the description covers only two parameters and gives no guidance on idempotency, error conditions, or the interplay of amount/contractPrice/franchisePercentageMargin. Too thin for the complexity of the call.

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 0%, so the description must carry parameter meaning. It does explain marginType as a name like 'FixedAmount' or 'Percentage' and flags carrierRouteId as required, but five of the eight parameters (amount, contractPrice, franchisePercentageMargin, intentId, externalLedgerCode) are left completely undefined — notably the relationship between the three monetary fields.

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 ('Add a partner shipping rate') and explicitly excludes customer-specific rates, which implicitly routes the agent to AddCustomRate. It also separates it from AddPartnerSurcharge by naming 'rate'. It stops short of a fully explicit sibling comparison, but an agent can place it correctly.

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?

The exclusion of customer-specific rates implies when to pick AddCustomRate instead, and 'Requires a carrier route id' gives a prerequisite. There is no explicit 'use this when / not when' statement and no mention of the required carrierContractId or how partner vs. custom scoping actually differs.

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