describe_lake

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

Annotations only declare readOnlyHint=true; the description adds substantial behavior beyond that: it is cheap and reads no data, it discloses live_mode where answers come from the vendor rather than the lake and are labeled as such, and it explains that coverage bounds are the mechanism for absence-vs-nonexistence. That is real operational context an agent cannot get from the annotation.

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-loaded with 'START HERE' and the core return contract before any routing detail. Despite being several sentences, each one carries load: return contents, coverage semantics, live_mode caveat, then the sibling routing table.

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?

No output schema exists, so the description carries the return-value burden and does so — it enumerates datasets, coverage window, history mode, freshness, and the query contract, plus live_mode. For a zero-required-param orientation tool, nothing an agent needs before calling 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?

Schema description coverage is 100% for the single include_empty parameter, and its own schema description already explains the empty-vs-unknown distinction. The description adds nothing further about the parameter, so the 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 (returns/describes) and resource (what this lake holds: datasets, coverage windows, history modes, freshness) plus the query contract. It is unmistakable against siblings like query_bars or run_sql, which retrieve data rather than describe the lake.

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?

Explicit 'START HERE' and 'Call it before answering anything factual about A-share data', with a concrete decision rule (use coverage_start/coverage_end to separate 'no such data' from 'did not happen'). It then names each alternative tool and the condition that selects it (resolve_symbol for names, query_bars for prices, query_fundamentals for financials, query_dataset for everything else, run_sql for aggregation).

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