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

With no annotations, the description carries the full burden. It partly meets it by disclosing output behavior (itemized cost breakdown plus net/ROI/annualized ROI/profit-per-hour and a verdict) and how unknowns are handled ('Unknowns are null and listed as unverified'). It never says the tool is a pure non-mutating calculation with no external side effects, nor how defaults are applied for omitted optional inputs.

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?

Two front-loaded sentences with no filler: the transaction model comes first, then the computation outputs. The output enumeration is long but earns its place because there is no output schema to describe return values.

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?

Given 31 parameters, no annotations and no output schema, the description does well on return values but poorly on inputs, which is the dominant risk for a tool this wide. An agent could invoke it with the four required fields, but would have little idea which of the 27 optional fields materially change the verdict.

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 only 16% across 31 parameters, so the description must compensate, and it largely does not — it never explains buyChannel, sellChannel, payoutMethod, comcService, the 90-day/120-day flags, or the various transit-day fields. It only vaguely maps to a few concepts ('buy fees, extraction, shipping, handling time, sell fees, payout'), leaving most inputs undocumented in both places.

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?

It states a concrete action (simulate buying on one marketplace and reselling on another) and enumerates the exact metrics produced, so the agent can tell this is a full ROI/profitability model rather than a fee lookup. It does not, however, distinguish itself from the siblings calculate_fees and best_place, so differentiation is missing.

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?

There is no explicit when-to-use guidance: nothing says to call this instead of calculate_fees or best_place, nor any prerequisite for the four required inputs. The only usage-adjacent note is the parenthetical 'A may equal B', which clarifies an edge case but not the selection decision.

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