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

Annotations declare readOnlyHint=false and destructiveHint=false, so the agent knows this is a non-destructive mutation. The description adds the partial-update semantic (only changed fields are submitted), which is genuinely useful context beyond the annotations. It does not disclose permission requirements, reversibility, or what happens when a field is omitted, leaving gaps for a mutation tool.

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 short sentences with zero filler: the first states what is updated, the second states how to call it. The key calling convention is front-loaded and nothing is redundant.

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 no output schema, the description covers purpose and the partial-update mechanism, and annotations cover the safety profile. It omits who may update a listing, whether updates are reversible, and the response shape, so it is adequate but not complete.

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 all six parameters are already documented in the schema, establishing the baseline of 3. The description's "pass only the fields you want to change" clarifies the partial-update contract across all optional parameters, adding modest value beyond the per-field schema descriptions.

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 names a specific verb (Update), resource (supplies/materials listing), and enumerates the kinds of fields affected (price, stock status, description). It is clearly distinguishable from marketplace_create_listing and marketplace_delete_listing, though it does not explicitly name those siblings.

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?

"Pass only the fields you want to change" gives useful partial-update guidance, which is implied usage context. However, there is no explicit when-to-use vs. when-not guidance, no mention of prerequisites (e.g., ownership of the listing), and no reference to sibling tools like marketplace_create_listing or marketplace_get_listing.

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