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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered. The description adds real value beyond that: the upstream source (FFIEC Call Report Schedules RI and RC-K) and, critically, the units — thousands of dollars for amounts and percentages for ratios — plus the presence of MDRM line codes, which prevents misreading the output.

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?

A single front-loaded sentence enumerating output contents, followed by the source citation and units note. Dense but every clause carries information; the only mild weakness is the fragment-style grammar that reads more like a feature list than a description.

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 no output schema, the description must carry the return-shape burden, and it does by enumerating the analysis components and naming the units. What remains thin is guidance on when this versus neighboring analysis tools is appropriate, which for a 3-param analytical tool is a moderate rather than critical gap.

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%, so all three parameters (rssd_id, peers, quarters) are already documented in the schema. The description only gestures at peers via 'history and peers' and adds no syntax, defaults, or interaction detail beyond what the schema provides, so the baseline of 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?

The description names a specific analytical resource (net interest margin) and enumerates exactly what it decomposes: each earning asset's balance/yield/contribution, each funding line's balance/cost, and the volume/rate decomposition of margin movement. An agent can distinguish it from generic siblings like profitability_analysis, though it never names an alternative explicitly.

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?

Usage is implied by the content listing — you call this to break NIM into earning-asset and funding-line contributions with history and peers. There is no explicit when-to-use/when-not statement and no routing to sibling tools such as peer_analysis or profitability_analysis, leaving the agent to infer the boundary.

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