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

Annotations already declare readOnly=true, openWorld=false and destructive=false, so the safety profile is covered. The description adds genuine behavioral context beyond that – the guide is dated, Ontario-specific, reviewed by an Ontario mortgage agent, and ships with a public source, review status and follow-up questions. Some of this overlaps the output schema, which caps it below 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?

Two dense sentences: the usage condition first, then return characteristics, then exclusions. No filler, and the front-loaded 'use this when' clause makes scanning easy. The long topic list is verbose but functional rather than wasteful.

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 read-only, closed-world, 2-enum-param tool with an output schema, this is complete. Usage boundaries, topic scope, provenance, and explicit exclusions are all present; return-value detail is largely delegated to the output schema as expected.

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% and both parameters are enums already documented in the schema. The description re-enumerates the nine topics in prose and implies 'short' maps to the brief detail mode, but adds no syntax or meaning beyond the schema. Baseline 3 is appropriate.

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 (read/retrieve) and resource (a short, dated Ontario mortgage preparation guide), and enumerates the nine supported topics. The 'not a calculation' qualifier cleanly distinguishes it from calculation-oriented siblings like compare_break_or_stay and plan_mortgage_prepayments.

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 states when to use ('user asks how to prepare for or understand a supported Canadian mortgage topic and is not asking for a calculation') and gives a detailed when-not-to-use list: general financial/legal/tax advice, current rates, arbitrary URLs, live web search.

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