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

Annotations already declare this a read-only, idempotent, non-destructive, closed-world computation, which is the full safety profile for a pure projection tool. The description adds one genuine behavioral fact beyond that – it emits suggested tiering thresholds, not just volumes – but says nothing about cost units, sensitivity assumptions, or how hot/cold tier prices drive the relative-cost 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 dense sentence with the resource and the key drivers front-loaded; nothing is padded. The semicolon-joined output clause is slightly compressed, but no sentence is wasted.

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?

An output schema exists, so return values need not be described. However, for a 9-parameter, 7-required financial projection with zero schema coverage, missing unit/semantics guidance for hotDays, months, and the two tier prices leaves real ambiguity about what a caller should pass.

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 0%, so the description carries the burden, and it only partially does: the named factors map cleanly to dailyIngestGB, retentionDays, compressionRatio, replicationFactor, and monthlyGrowthPercent. It leaves months, hotDays, hotTierPricePerGBMonth, and coldTierPricePerGBMonth (4 of 9 params) entirely unexplained, including the hot/cold tiering boundary that the tool's headline feature depends on.

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: 'Project storage volume and relative cost over time' plus the five modeling inputs (ingest, retention, compression, replication, growth) and the tiering-threshold output. An agent knows exactly what computation this performs. It does not name or distinguish itself from adjacent siblings like capacity_plan, cost_model, or finops_unit_economics, so it falls short of a 5.

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?

There is no explicit when-to-use guidance, no exclusions, and no routing to alternatives in a sibling set that contains several plausible overlaps (capacity_plan, cost_model, finops_unit_economics). Usage is only inferable from the modeled factors themselves.

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