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

Beyond annotations (readOnly, idempotent, non-destructive, closed-world), it adds a real prerequisite — 'Requires the send_planner.view permission' — and, in the absence of an output schema, discloses the exact figures returned (units per network, units short, SKUs short, units left at source, stockouts before arrival, 2-day reach). It does not mention result size limits or failure behavior, keeping it below a 5.

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 tight sentences, front-loaded with the operation and scope, then the filter, then the permission requirement. The metric list is dense but every item carries information the agent cannot get from structured fields.

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 read-only comparison tool with no output schema, the description supplies the missing return-value picture, the cardinality limit, the optional filter's semantics, and the permission gate. Nothing an agent needs to select and invoke it correctly is absent.

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 both parameters are already documented, and the description mostly restates the schema's constraints ('one to four', 'base plan first'). The phrase 'across the plans' slightly sharpens product_id's scope, but that is a marginal addition over the schema text.

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 and resource: 'Compare one to four send plans side by side,' and enumerates the compared metrics, so the agent knows exactly what the tool produces. It does not explicitly name a sibling it is not (e.g., get_send_plan for a single plan detail, explain_send for narrative explanation), leaving differentiation partly implicit.

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 concrete context for the typical call ('the working plan and its scenarios') and explains the optional filter's purpose ('Pass product_id to compare a single product across the plans'). It stops short of stating when to prefer this over get_send_plan or explain_send, so there are no explicit exclusions.

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