AWS OpenSearch MCP Server

explain_unassigned_shard

Analyze why a shard remains unassigned in an Amazon OpenSearch Service domain, returning allocation decisions and reasons for the first unassigned shard or a specific shard by index, shard ID, and primary status.

Instructions

Explain the first unassigned shard, or a specific shard when all shard fields are given.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "profile": "<profile>",
      "region": "<region>",
      "domain": "<domain>"
    },
    "name": "explain_unassigned_shard"
  }
}

Input Schema

Name	Required	Description	Default
`index`	No
`shard`	No
`domain`	Yes
`region`	Yes
`primary`	No
`profile`	Yes
`include_yes_decisions`	No

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Jul 8, 2026

TDQS

B3.3/5.0

Behavior2/5

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

With no annotations provided, the description only states the action ('explain') without disclosing behavioral traits such as whether it is read-only, required permissions, side effects, or output format. This is insufficient for an agent to assess operational impact.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single sentence that front-loads the purpose. It is concise, though it could benefit from slightly more detail without becoming verbose.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given 7 parameters, no schema descriptions, no annotations, and a conceptually complex topic (shard explanation), the description is too minimal. It fails to define 'explain', describe the output schema, or provide enough context for correct agent invocation.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, so the description must compensate. It adds meaning by indicating that providing 'all shard fields' triggers specific shard mode, but does not list which parameters compose those fields or explain their roles, leaving ambiguity for the agent.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool explains an unassigned shard, distinguishing between the first unassigned or a specific shard when all identifying fields are given. This differentiates it from sibling tools like diagnose_cluster or get_shard_allocation.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies two usage scenarios (first unassigned vs specific shard), but provides no explicit guidance on when to prefer this tool over alternatives or prerequisites. Context from sibling tools is not addressed.

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