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

Annotations already cover the read-only and open-world profile, and the description adds genuinely useful context beyond them: a $0.05 USDC charge per successful call via x402 on Base or Solana, and that an API key bypasses this. It does not state rate limits or failure/refund behavior, so not 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?

Two compact sentences with the capability front-loaded and the payment caveat trailing. Every clause carries information; the only mild inefficiency is enumerating return fields rather than summarizing them.

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?

A single-parameter read-only lookup with no output schema is well served here: the description names the returnable fields (server name, member counts, server tag, inviter, creation date, invite expiry) and the cost model. Only the ambiguity about which sibling handles usernames/tags is unaddressed.

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% and the single 'query' parameter is already documented as 'Invite code (or discord.gg link code), or a numeric user, bot or server ID'. The description restates the same accepted formats without adding syntax, validation, or example details, so baseline 3 applies.

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 (look up) and resource (Discord invite code or numeric user/bot/server ID) plus the fields returned. It implicitly separates itself from discord_username/discord_tag/discord_server_search by restricting input to invites and numeric IDs, but never names those siblings so the agent must infer the boundary.

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: the input type (invite code or numeric ID) hints that username/tag searches belong to other tools, but no explicit when-to-use or when-not-to-use statement is given. The pricing note tells the agent about cost, not about choosing this tool over alternatives.

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