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

Goes well beyond annotations by disclosing the verification lifecycle ('listed as unverified until ARC re-runs a sample'), a concrete rate limit ('5 per network per day'), a hard precondition ('runs must stop before payment'), and cost ('Free'). These are exactly the behavioral traits an agent cannot infer from readOnlyHint/destructiveHint/idempotentHint.

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?

Six short sentences, all front-loaded with the core action first, then constraints. Every sentence carries information (cost, verification, format, precondition, limit, API mapping); a minor nit is that the format/API-mapping details could be consolidated, but nothing is wasted.

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 write tool with no output schema, six parameters and nested objects, the description covers the submission preconditions, rate limit, and verification outcome that an agent needs to call it correctly. It omits auth requirements and failure behavior, but the essential calling constraints are present.

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 description coverage is only 17%, so the description must carry most of the parameter burden, but it only clarifies the spec constant and the stopped_before_payment precondition. It says nothing about the results array shape, the 10–100 item bounds, the agent.path enum, or optional contact handling, leaving the low-coverage schema uncompensated.

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 and resource — 'Submit your agent's run against ARC-100 v1 to ARC's open leaderboard' — which unambiguously separates it from read-oriented siblings like agent_leaderboard. The API mapping ('Same as POST /api/leaderboard/submit') further pins down the exact operation.

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?

Gives clear context for use: run against ARC-100 v1, must stop before payment, format arc-leaderboard-submission/v1, and a daily cap. It stops short of explicitly naming alternatives (e.g. agent_leaderboard for reading results) or stating when NOT to submit, so it is clear but not fully routing.

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