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

Annotations already declare readOnlyHint=false and destructiveHint=false. The description adds value beyond them by scoping the side effect ('changes only your own list, so it runs without asking') and by disclosing an auth requirement (Cotlet API key with app access). This is real context an annotation cannot carry.

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 and short, but the first two sentences are near-duplicates ('Follow the value of any home ... on the market or not' / 'Adds a home to the homes whose value you follow, for sale or not'), which wastes space without new information.

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 one-parameter mutation with annotations and no output schema, the description covers effect scope, listed/unlisted applicability, the absence of an unfollow counterpart, and auth needs. Little an agent needs in order to call it is missing, though the follow-vs-save distinction remains unaddressed.

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?

One required parameter with 100% schema description coverage, including the expected address format, so the schema does the heavy lifting. The description only restates that lookup is 'by address' without adding syntax or format meaning, matching the baseline-3 case for high coverage.

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 (follow the value of a home) and a scope qualifier ('on the market or not'), so an agent understands this watches a valuation rather than just bookmarking. It does not explicitly differentiate from the sibling hemnet_save_home, which is the nearest-looking alternative, so it stops 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?

Gives usable context: works whether or not the home is listed, and it makes clear that the inverse operation has no tool ('Unfollowing is done in the Hemnet app'), which prevents an agent hunting for a remove_follow. It never states the condition that selects this over hemnet_save_home, so no explicit when-to-use-vs-alternative.

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