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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds genuinely useful behavioral context beyond that: that rendered content is NOT returned (an important negative disclosure) and that declared variables are the ones to populate in `vars` on send.

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?

A single front-loaded sentence with a parenthetical; no filler, no restating the title, and the most decision-relevant fact (lookup by slug, what you get) comes first.

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?

An output schema exists, so return-value detail is optional, and the safety profile is covered by annotations. Naming the correct sibling for slug discovery (templates_list) would make it fully complete, but nothing needed to call the tool correctly is missing.

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%, including a detailed spec for the `context` analytics parameter, so the schema carries the parameter burden and the baseline is 3. The description reinforces the slug lookup but adds no syntax or format detail for either parameter; the `vars` hint refers to a different tool's field rather than this tool's inputs.

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 and resource ('Look up a template by slug') and enumerates exactly what is returned: channel, status, version number, publish time, declared variables. This is clearly distinguishable from senderkit_templates_list (discovery) and senderkit_templates_create/regenerate (mutation) without opening another schema.

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 parenthetical 'fill these in `vars` when sending' implies the downstream workflow, and 'by slug' implies the caller already has a slug. But there is no explicit when-to-use vs templates_list (find a slug) or templates_regenerate (change content), and no stated prerequisites, so usage is only implied.

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