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

Annotations already declare readOnlyHint=true and idempotentHint=true, but the description adds meaningful behavior beyond those: it 'validates applicability without revealing the filing value, comparison source value, later revision values, evidence, or arithmetic.' This tells the agent the tool intentionally withholds sensitive outputs, which is critical for setting expectations. It also states the operation is free, a useful cost signal. No contradiction with annotations.

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?

Three sentences, each earning its place: the first defines the tool, the second details when to use it and what it withholds, the third routes to alternatives. It is front-loaded with the core purpose and uses a compact list to avoid vague prose. No filler or repetition.

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 tool with 12 parameters and an output schema, the description covers the essential operational context: relationship to the paid reconcile operation, the uncertainty triggers, the privacy behavior, and sibling routing. It doesn't explicitly state what the eligibility result looks like, but the output schema already covers return values. A slight gap is not defining 'eligibility' precisely (e.g., what a true/false result means for downstream calls), which would push it to a 5.

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 the baseline is 3 per the rubric. The description indirectly references the parameter categories ('issuer identity, filing selection, supported metric, fiscal-period dates, annual-versus-quarter context, required SEC Company Facts contexts, or an optional SEC-filed 8-K earnings-release number comparison') which map to identifier/cik, anchor_accession, metric, period_start/end, period_type, and comparison_* fields. However, it adds no concrete semantics beyond what the schema already documents for individual parameters.

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: it is a 'Free eligibility check for filedproof.reconcile_financial_fact', which clearly identifies it as a prerequisite validation step for a named specialist operation. It also distinguishes itself from siblings by naming alternative tools (resolve_issuer, list_filings, search_evidence) for different use cases. An agent can tell exactly what this tool is for without needing to open other schemas.

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?

Explicitly tells the agent when to invoke it: 'Use this before the $1 specialist operation when ... may be uncertain', and enumerates the specific uncertainty dimensions (issuer identity, filing selection, metric, dates, period type, SEC contexts, 8-K comparison). It also gives clear exclusions: 'For general filing lookup or narrative research, use ... instead.' This is model guidance for tool selection.

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