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

Annotations already declare this is a non-read-only, non-destructive, non-idempotent mutation. The description adds that only changed fields should be supplied and that the operation is free, which is helpful behavioral context, but it does not explain effects such as whether renaming changes links or what archiving exposes.

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 and extremely concise: two short sentences cover the editable fields, the partial-update instruction, and cost. There is no filler.

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 five-parameter update tool with annotations and a partially documented schema, the description supplies enough field-level meaning and partial-update behavior for an agent to invoke it correctly. The main missing piece is explicit routing versus sibling tools, but that is not essential for basic invocation.

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 only 20%, so the description must compensate. It does so by naming the four optional editable fields — rename, description, postal address, and archive — though it does not clarify that 'archive' maps to the boolean public_archive or add constraints beyond those in the schema.

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 the resource indirectly via the title and lists the specific fields that can be changed: name, description, postal address, and archive. It is clear this updates an existing newsletter rather than an issue or a new newsletter, but it does not explicitly differentiate itself from siblings such as newsletters_create or newsletters_update_issue.

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 phrase 'Give only what changes' usefully signals a partial update and implies omitted fields are left unchanged. However, it does not state when to use this tool versus newsletters_create or newsletters_update_issue, nor does it mention prerequisites such as requiring an existing newsletter.

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