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

Annotations declare non-read-only, non-destructive, closed-world, but the description adds important behavior: duplicate names are rejected for disambiguation, an unlocked draw is regenerated automatically, and late arrivals are handled differently in americano vs mexicano. That is substantial context beyond the annotations.

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?

The description is dense but front-loaded with the core action and bulk constraint. The americano/mexicano detail is somewhat long, but each sentence contributes specific behavior.

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?

An output schema exists, so return values needn't be explained. The description covers the mutation's side effects and edge cases well, though it could say more about failure modes when a duplicate is rejected or about signup mode mechanics.

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 67%. The description explains that callers must parse lists themselves and send structured entries, and it mentions placeholder names and signup mode, which clarifies the players array semantics. It does not add much about request_id or tournament_key beyond what the schema already says.

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 states a specific verb (add) and resource (players) and adds scope ('in bulk') plus mode nuance ('signup mode when names aren't known yet') that distinguishes it from single-player siblings like promote_player.

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 clear usage context ('parse pasted lists or spreadsheets yourself', 'never invent placeholder names', 'use signup mode') but does not explicitly contrast with siblings such as update_player or replace_player or say when not to use this tool.

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