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

Annotations already declare this is a non-readonly, non-destructive, non-idempotent, closed-world write. The description adds meaningful context beyond that: the output is a draft (not sent), and the operation is free. It omits what happens on repeated calls (does it create a second draft or overwrite?) and whether sending requires the returned issue identifier, which matters given idempotentHint=false.

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?

Three short clauses, no filler, and the sequencing hint is placed up front. The opening is a noun fragment ('A draft issue in Markdown') rather than a complete statement of action, which costs it a point but the compactness is otherwise well judged.

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 4-parameter write tool with no output schema, the description should say what comes back (issue id/slug) since the recommended next step is newsletters_send_issue, and it should address whether drafts are versioned. Neither is covered, so an agent knows the workflow shape but not the handoff payload.

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 75% and the schema already documents body (Markdown features, length caps), preheader, and newsletter (slug or exact name); only subject is undocumented but self-evident. The description adds no parameter-level detail beyond 'Markdown', so the baseline 3 for a mostly-covered schema 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?

The definition makes clear this produces a draft issue authored in Markdown, and it distinguishes itself from newsletters_send_test and newsletters_send_issue by placing itself as the first step of that workflow. It never uses an explicit verb ("write"/"create") in the description body, relying on the title and sibling routing to convey the action, which keeps it short of a 5.

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 states the follow-on workflow: review with newsletters_send_test, then send with newsletters_send_issue. That is real routing guidance an agent can act on. It does not address when to prefer newsletters_update_issue over this tool or how to handle an already-existing draft, so it is not a full when/when-not treatment.

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