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

Annotations already cover safety (readOnlyHint) and reach (openWorldHint), and the description adds genuinely useful context beyond them: which fields are conditional ('if public'), the presence of ban flags, and the x402 payment model including the 'per successful call' qualifier. It stops short of describing not-found/error behavior.

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; the payload of identifiers and returned fields comes first and the cost note is correctly demoted to the end. Slight waste in the awkward 'Any Steam account with all its ID formats' opener, but nothing extraneous.

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 carries the burden of describing the response and does so by enumerating the profile fields, including conditional ones. Remaining gaps are minor: no mention of failure/not-found behavior or billing on failed lookups.

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 schema description already lists SteamID64, STEAM_0:Y:Z, [U:1:N], custom URL and profile link. The description largely restates those formats, adding no syntax or edge-case guidance beyond what the schema provides, 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?

The description names the resource (Steam account) and enumerates the returned data (IDs, name, avatar, real name, country, member since, ban flags), which clearly separates it from siblings like discord_lookup or username_scanner. It lacks an explicit verb ('look up'/'retrieve'), reading as a noun phrase, but the intent is unambiguous.

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 implied by the enumeration of accepted ID formats, and the pricing note ('without an API key: $0.05 USDC per successful call') hints at an authenticated free path. However, it never states when to prefer this over alternatives such as username_scanner or osint-username, nor any prerequisites.

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