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

Annotations only declare destructiveHint=true and readOnlyHint=false; the description goes well beyond by explaining that the rate is shared not copied, that later edits to the rate propagate to this group, that the rate is appended last in charging order, that merchant confirmation is required, and that past sales are not recalculated. This is exactly the side-effect context an agent needs for a destructive mutation.

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?

Six short sentences, each carrying distinct, load-bearing information (scope, id source, sharing semantics, alternative tool, ordering, confirmation/retroactivity). The most important constraints — eligibility and side effects — are front-loaded rather than buried.

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 destructive, non-read-only mutation with no output schema, the description covers prerequisites (existing rate, ids from get_taxes), propagation semantics, ordering behavior, and retroactivity limits. Nothing material an agent needs to invoke it safely is missing.

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%, so taxRateId, taxGroupId, and compounding are already documented in the input schema, establishing a baseline of 3. The description adds the useful nuance that compounding is modifiable and that ids come from get_taxes, but repeats rather than extends the schema's per-parameter definitions.

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 an EXISTING rate to a tax group') plus a secondary modification mode (changing that rate's compounding flag). The word EXISTING and the contrast with create_tax_rate make it immediately distinguishable from hub_create_tax_rate, hub_remove_tax_rate_from_group, and hub_update_tax_group.

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 routing: use create_tax_rate when the rate does not exist yet, and use update_tax_group with rateIdsInOrder to reposition an already-added rate. It also names the source of both ids (get_taxes), so an agent knows the prerequisite lookup.

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