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

Annotations already declare readOnlyHint=true, so the description is not carrying the safety burden. It still adds genuine value beyond the annotations: 'Passwords are redacted' discloses a non-obvious property of the returned payload, and the trailing 'Civo: GET /v2/instances/{id}' pins the underlying operation. It says nothing about auth requirements, error cases, or pagination, so it falls 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?

A single dense sentence that is front-loaded with the verb and the payload highlights, followed by a short API reference. Every clause carries information; the only mild cost is a long comma-delimited field list that reads as inventory rather than prioritised prose.

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?

With no output schema, the description is right to enumerate the returned fields, and both parameters are fully documented by the schema. What is missing is the idiosyncratic behavior of the response (what happens for a nonexistent id, whether the redaction affects any other fields), so it is strong but not exhaustive.

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 the region default (CIVO_REGION) and the regional-resource caveat, so the schema already does the heavy lifting. The description adds no parameter-level meaning (it never mentions instance_id or region), which is exactly the baseline-3 case.

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 ('Fetch one instance') and then enumerates the returned attributes (status, size, CPU/RAM/disk, IPs, network, firewall, tags, volumes, source image), which makes it unambiguous versus the sibling civo_list_instances. An agent knows exactly what class of tool this is 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?

Usage is only implied: fetch by id when you already have the instance id. There is no explicit when-to-use/when-not, no mention of civo_list_instances as the discovery alternative, and no stated prerequisite about needing the id first. Adequate but leaves routing to inference.

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