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

Annotations only declare the write/safe/open-world profile; the description adds the crucial two-phase behavior — nothing happens until the intent is signed and submitted. That is exactly the kind of context an agent cannot infer from readOnlyHint=false alone, and it prevents the agent from assuming the cart is mutated immediately.

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 sentences, front-loaded with the action and its arguments, followed by the operational caveat. No filler; every clause carries information.

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 mutation tool with full parameter documentation, annotations covering the safety profile, and no output schema, the description supplies everything needed: the action, its inputs, and the sign/submit lifecycle. Nothing essential 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 description coverage is 100%, so signer, quantity, and add_item_id are already documented in the schema. The description restates 'by id' and 'with a quantity' and reinforces that the intent is prepared for `signer`, but adds no format or constraint detail beyond the schema. Baseline 3 is appropriate.

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 product or service ... to your Marketplace cart') plus the two key qualifiers (by id, with a quantity). This clearly distinguishes it from siblings like geode_market_update_cart_item_quantity and geode_market_remove_item_from_cart.

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 clear workflow context: it prepares an unsigned transaction for `signer` and routes the agent to geode-local-signer for signing and geode_submit_intent for submission. It stops short of explicitly stating when to choose this over update_cart_item_quantity (new item vs existing item), so it lacks a true exclusion.

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