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

Goes well beyond the readOnly/idempotent annotations: discloses the X-API-Key auth mechanism, tier gating, that failures surface as isError, that missing or stale inputs are reported as unavailable rather than imputed, and explicitly bounds the semantics (descriptive only, no causal attribution or anomaly probability). That is exactly the extra context annotations cannot carry.

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?

Front-loads the return payload, then auth, then semantic caveats — a sensible ordering. It is dense and a couple of clauses (the pricing URL, the disclaimers list) run long, but every sentence carries distinct information.

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 an output schema already describing return structure and annotations covering safety, the remaining burden is auth, failure modes, and interpretive limits — all of which the description supplies. Nothing an agent needs to call this correctly is missing.

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?

The tool takes no parameters, so the baseline is 4; the description correctly implies there is nothing to configure. It adds no parameter information because none is needed.

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 concrete verb ('Returns') and enumerates the exact payload: scheduled Hodge and lag-relation snapshots, coverage, observation times, invariants and timestamped history across named cohorts. This is clearly distinguishable from siblings like get_hodge_regime_sieve or get_network, which cover narrower slices.

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?

Explicitly names the prerequisite (paid-tier API key with the engines capability) and warns that the free key from register_agent will be refused, which is a genuine routing signal. It does not, however, say when to prefer this over the more targeted siblings such as get_hodge_regime_sieve.

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