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

Annotations already declare idempotentHint=true, but the description adds the concrete consequence ('adding an email that already exists just updates its name') plus the account-level scoping that annotations cannot express. It stops short of covering error behavior (e.g. invalid email) but adds genuine value over the structured fields.

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 sentences, zero filler, with the core purpose and scope front-loaded before the idempotency detail and the sibling pointer.

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 two-parameter account-level write with no output schema, the description covers purpose, scope (account-wide, not product-scoped), idempotency, and the follow-up tool. Nothing an agent needs in order to invoke it 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% with only two simple parameters, so the schema already documents both email and name. The description adds only the idempotent-update semantics for name, which is a marginal gain; baseline 3 applies.

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+resource ('Save a test recipient') and immediately defines it in parenthetical terms ('an address you send preview/test emails to'), so an agent can distinguish it from the real-contact siblings like meisa_add_contact.

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?

Gives clear context (preview/test emails) and routes the agent forward to meisa_send_template_to_test_recipients. It does not, however, explicitly say when to prefer this over meisa_add_contact or meisa_upsert_contact, which is the more likely confusion given the sibling list.

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