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

With annotations declaring mutation (readOnlyHint=false, destructiveHint=true), the description adds real context beyond them: the photo never leaves to Dashly, the result is a 'friendly likeness, not a portrait,' and renaming only occurs on request. It stops short of stating that the existing companion is replaced/overwritten, which the destructiveHint implies.

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 front-loaded paragraph that leads with what changes and where, then the branch rules. It is dense but every sentence carries a rule (rename gating, photo privacy, default naming); a little more structure would improve scannability.

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 no explanation. For a 3-param tool with a nested spec object and no required params, the description covers the person-vs-animal paths, privacy handling, and naming rules well; the one gap is not spelling out the replacement/destructive effect on the current companion.

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 coverage is 67%, and the description compensates usefully: it explains the name parameter's two modes (rename vs. auto-assigned for a new animal like Pip/Bao/Lumi) and that the spec is drawn from fixed lists based on a photo. This adds semantics the schema alone does not convey.

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 (Changes) and resource (the companion), and goes further to say where it appears: status tile, calendar, and when they log. It also names the concrete values (Pip, Bao, Lumi, or a person) so an agent knows exactly what this tool manipulates.

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 conditional guidance — 'Pass a name alone to rename it (only when the person asks)' — and a workflow for the person case (look at a shared photo, fill spec from fixed lists). It lacks explicit exclusions against sibling tools, but no sibling touches the companion, so routing ambiguity is low.

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