Cmc Listings

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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so safety is covered. The description adds genuinely new context about auth ('API key is resolved server-side, never accepted as an argument'), which usefully tells the agent not to hunt for a credentials parameter, but says nothing about pagination, result size, or how 'delta' mode behaves.

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 front-loaded statements with no filler: purpose, exclusion/alternative, auth note. The only blemish is the awkward hard-wrapped line break mid-clause, which slightly hurts scanability but not content density.

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 need no explanation, and annotations cover the safety profile. But with 0% parameter documentation in the schema, the description leaves mode=delta and source_checkpoint completely undefined, which is a material gap for an agent trying to call this correctly.

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 0% across four parameters, so the description carries the full burden and fails: mode's empty/'delta' enum, start, limit, and especially source_checkpoint (an opaque anyOf object) are never explained. Only the generic listing semantics weakly imply what limit/start do.

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 first line names a specific resource and ordering ('cryptocurrency listings ranked by market cap') and parenthetically frames the scope as discovery/caps. It separates itself from a market-data feed, though it never distinguishes itself from the near-name siblings cmc_quotes and cmc_global_metrics.

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?

'Not a venue-specific OHLCV feed — use an emerald-exchange backend for tradable bars' is an explicit when-not plus an alternative, which is strong routing guidance. The gap is that the alternatives it names are outside the sibling set, while the actual siblings (cmc_quotes, cmc_global_metrics) go unaddressed.

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