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

Adds behavior annotations don't cover: the day-over-day vs week-over-week comparison basis, the 50-ticker cap, the per-change shape {field, from, to}, tier-gated extras (Plus and Pro get stability, periods_in_current_state, recent flips), and that ticker_context carries last_changed_date. Since an output schema already exists, describing return fields is partly redundant, which keeps this from a 5.

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 core operation, then moves to response shape, tier differences, and the sibling routing rule. Dense but nearly every clause carries information; the response-shape sentence is the only part that overlaps with the output schema.

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 two-parameter read tool with full schema coverage, annotations, and an output schema, the description covers purpose, alternatives, response structure, tier gating, and the companion ticker_context payload. Nothing needed to invoke it 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?

Schema coverage is 100% and already documents both parameters, including the daily/weekly enum and the 50-item cap. The description restates the same semantics ('day-over-day for daily, week-over-week for weekly') without adding syntax or edge-case guidance, so this sits at the baseline.

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 ('get field-level band changes'), scopes it ('newest published date, up to 50 tickers'), and immediately contrasts with get_summary. An agent can distinguish it from every sibling without opening a schema.

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 an explicit example utterance ('what changed for AAPL, MSFT and NVDA today?') plus a negative instruction ('instead of pulling full summaries') and names the alternative tool with the condition that selects it ('use get_summary for one ticker's full state').

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