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

Annotations already declare readOnlyHint=false, idempotentHint=false, and destructiveHint=false; the description adds real value on top by spelling out the consequence of non-idempotency (a retry silently creates a duplicate) and the post-creation state (no followers yet, so add_follower is required next). It doesn't say what the response contains after a successful create, and with no output schema that leaves a gap.

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, front-loaded with the resource definition, then the follow-up action, then the hard constraint and the retry hazard. No filler and nothing repeated from structured fields.

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 3-parameter creation tool with no output schema, the description covers the resource, its empty starting state, the master eligibility rule, and duplicate-creation risk. The main remaining gap is the return value and how to identify the newly created copier, which matters because the agent cannot otherwise confirm success without calling list_copiers.

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 coverage is 100%, so the baseline is 3, but the description adds an eligibility constraint on master_id beyond the schema text: the master must be a hedging account (all MT4, MT5 hedging only), which the schema does not state. It says nothing extra about name or is_active, so it's not a full 5.

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?

The description defines the resource concretely ('A copier copies one master account to its followers') and states the key initial state ('It starts without any: add them next'), which implicitly distinguishes it from add_follower. The creation verb itself is only carried by the title, not the description body, so it falls just short of a fully self-contained purpose statement.

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?

It gives an explicit prerequisite ('Masters must be hedging accounts (all of MT4, and MT5 hedging accounts)') and a concrete when-not-to-call warning ('Retrying a failed request can create a second copier; list your copiers first'), which routes the agent to list_copiers. It does not contrast with update_copier or say when a new copier vs. reusing an existing one is preferable, so it stops short of full alternative routing.

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