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

Annotations only declare non-readOnly, closed-world, and non-idempotent. The description adds material behavior beyond those hints: it leaves a pending offer with role 'buyer' and status 'pending', has no escrow or payment creation, and guarantees the response never reveals seller floor or fees.

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?

The description is front-loaded with WHEN and the resulting state, and most sentences earn their place. 'Barter offer.' redundantly restates the tool name, and the example largely duplicates the required-parameter schema, so it is efficient but not maximally tight.

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 5-parameter, no-output-schema mutation, it explains when to use it, what state is created, and the payment/privacy constraints. It does not clarify how the amount is determined when omitted or what errors/auth failures look like, but coverage is broadly adequate.

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 listing_id, key, note, and amount/amount_usd are already documented in the schema. The example reinforces use of listing_id but adds no syntax or meaning beyond what the schema provides, so the baseline 3 applies.

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?

Names the action ('makes an offer') and the target ('open cash listing'), and the title's 'Cash barter' separates it from code-offer siblings. However, the opening 'Barter offer' only restates the name and no sibling is named explicitly, so it stops short of a 5.

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 WHEN line scopes use to a registered buyer acting on an open cash listing. It provides clear context but no when-not-use guidance, additional prerequisites, or named alternatives.

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