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

Annotations already indicate this is not read-only and not destructive. The description adds the important behavioral detail that the tool acts as an upsert and supports partial updates, which goes beyond the annotations. No annotation contradiction is present.

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 two short sentences with no redundant wording. The most important behavior, create versus update, is front-loaded, and the instruction about passing only changed fields is immediately useful.

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?

The description covers the core upsert behavior and partial updates, and the schema documents every parameter. However, there is no output schema and the description does not mention return values, required fields for creation, validation, or error behavior, leaving moderate gaps for an 18-parameter tool.

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?

The input schema has 100% description coverage, so all 18 parameters are already documented individually. The tool description only reiterates the counterparty selector behavior and the partial-update principle without adding new parameter-level meaning, which matches the baseline of 3.

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 clearly states the tool creates a new counterparty when no counterparty is specified and modifies an existing one when it is. It uses a specific verb and resource, and the create/update distinction separates it from sibling tools like counterparties_list and counterparties_delete.

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 description gives clear usage context: omit counterparty to create, include it to update, and pass only fields that should change. It does not explicitly name alternatives or state when not to use the tool, so it stops short of a 5.

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