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

Annotations already declare the safety profile (idempotent, non-destructive, not read-only). The description earns credit for going beyond them with partial-update semantics and the merge-not-replace behavior for custom fields, which prevents accidental data loss assumptions. It does not cover auth/permission requirements or conflict handling, keeping it short of a 5.

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?

Front-loads the operation, then the partial-update rule, then usage guidance and the prerequisite. Every sentence is functional, though the merge detail is stated both here and in the schema, a small redundancy.

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 an 8-parameter mutation with a nested object, full schema coverage, and no output schema, the description supplies the key behavioral facts an agent needs (partial update, merge, UUID prerequisite). The main remaining gap is not distinguishing itself from meisa_upsert_contact.

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 the baseline is 3. The description reinforces the custom_fields merge behavior, but that same fact is already stated in the schema's custom_fields description, so it adds little beyond the structured data.

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 (update) and resource (existing contact), and adds semantic detail: only provided fields are changed, omitted fields untouched, custom fields merged. This clearly separates it from a generic write. However, it does not name its closest sibling meisa_upsert_contact, so the agent must infer the update-vs-upsert boundary itself.

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 explicit when-to-use context ('when the user wants to change a contact's name, status, tags, or custom attributes') and names the prerequisite alternative meisa_search_contacts for obtaining the UUID. It stops short of stating when NOT to use it (e.g., creating a new contact or upserting), which is the natural counterpart sibling.

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