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

Annotations already declare the safety profile (readOnlyHint=false, destructiveHint=false, idempotentHint=false). The description adds context beyond that: the 409 duplicate-email conflict behavior and the routing to meisa_upsert_contact for idempotent cases. It does not, however, cover side effects like auto-creating tags or permission/auth requirements.

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 sentences, each carrying distinct load: purpose, usage constraint, error/alternative behavior, and return value. The primary purpose is front-loaded with the guidance following.

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 single-resource create tool with annotations covering the safety profile and a fully documented schema, the description supplies the two remaining unknowns an agent needs: the duplicate-email failure mode and the returned object. No output schema is needed given the return value is stated.

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%, so every parameter (including the enum, defaults, and the auto-tag-creation note) is already documented in the schema. The description adds no parameter-level syntax or format detail, so the 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 and resource ('Create a new contact in Meisa') and immediately distinguishes itself from the sibling alternatives meisa_upsert_contact and, implicitly, meisa_update_contact. An agent can identify the operation without opening the 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?

Explicit when: 'only when the user explicitly asks to add a new subscriber or contact'. Explicit failure branch and alternative: on 409 duplicate email, 'use meisa_upsert_contact instead'. Both the usage condition and the fallback tool are named, leaving nothing to inference.

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