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

Annotations only declare destructiveHint=true; the description goes further by disclosing the ambiguity around omitted fields on update and prescribing a workaround (send the full record). It does not cover auth requirements, error behavior, or whether an update can clear existing fields, but it adds real behavioral value beyond the annotation.

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 tightly written sentences that lead with the mode switch and immediately follow with the critical caveat; nothing is padded. The trailing 'Loyverse: POST /suppliers/.' is a minor, format-conventional addition rather than a load-bearing sentence.

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 13-parameter upsert with no output schema and a destructive annotation, the description covers the two things an agent must know: how to pick create vs update and the partial-update risk. Missing only finer details such as uniqueness of `name` or what an update returns.

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 all 13 parameters are already documented. The description's mention of `id` driving create-vs-update duplicates the schema text ('Existing supplier id to update. Omit to create.'); only the full-record advice is new, so 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 pair and resource ('Create a supplier, or update one by passing its id') with the exact mechanism that switches between the two modes. No sibling tool writes suppliers, so the distinction from loyverse_list_suppliers and the other upserts is unambiguous.

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?

Explicitly tells the agent how to choose the update path (pass `id`) versus the create path (omit it), and adds the operational rule to send the full record on update. It stops short of naming alternatives or exclusions, but the when-to-use guidance is concrete.

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