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

Goes well beyond the readOnly/idempotent annotations: amounts are never converted, published values are frozen while revised_* carries later corrections, coverage_affected/coverage_note flag skewed baselines, minimum sample sizes (5) are stated, and unknown arguments are rejected. This is unusually rich behavioral context for a read tool.

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 the resource, then arguments, then index mechanics, then caveats. Dense but each clause carries information. The methodology/field-name sentences (revised_*, coverage_note) are the least economical, though they stand in for a missing 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?

With no output schema, the description usefully names output concepts (Count Index formula, USD median index needing 5 rounds, revised_*, coverage_affected, coverage_note). It is nearly complete, though the exact response envelope/field layout is still unspecified.

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 already 100%, so baseline is 3, but the description adds real meaning: the 'YYYY-Www' format with a concrete example ('2026-W39'), the omit-for-latest behavior, and the 1–104 range for weeks. Marginal value above the schema.

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+resource: 'Get ... the weekly Builders Fintech Funding Index of approved equity rounds (ISO weeks)'. The resource is narrowly scoped and clearly distinct from siblings like funding_summary or largest_rounds, which do not produce an index.

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?

Explains the two usage modes precisely: pass 'week' to get a specific ISO week, omit it to get the latest weeks newest-first, with 'weeks' controlling quantity. It does not explicitly name an alternative sibling or say when to prefer this over funding_summary/largest_rounds, so it stops short of a full when/when-not statement.

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