Server Quality Checklist

Tool Scores

• list_sessionsA
  4.2/5.0
  Behavior4/5

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

  Annotations already declare readOnlyHint=true, and the description adds a key behavioral constraint: returns only counts, never message content. This goes beyond the annotation by clarifying the data privacy boundary, which is valuable for an agent deciding whether to use this tool.

  Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

  Conciseness5/5

  Is the description appropriately sized, front-loaded, and free of redundancy?

  Two sentences, front-loaded with the action and result contents, followed by usage examples and a boundary statement. Every sentence earns its place with no redundancy or fluff.

  Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

  Completeness4/5

  Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

  The description is complete for a read-only list tool, covering the return shape and privacy boundary. It lacks an explicit note on defaults (e.g., limit behavior) but given the schema documents all parameters and no output schema exists, the description provides sufficient context for an agent to use the tool effectively.

  Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

  Parameters3/5

  Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

  Schema description coverage is 100%, so all parameters (limit, since, until, project) are already documented. The description adds no additional parameter-level meaning beyond what the schema provides, so a baseline score of 3 is appropriate.

  Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

  Purpose5/5

  Does the description clearly state what the tool does and how it differs from similar tools?

  The description clearly states the tool lists past Claude Code sessions with specific attributes (newest first, project, time span, turns, prompts, token usage, tool tally). This distinguishes it from siblings like session_stats and tool_usage by focusing on session listing rather than aggregate stats or tool usage alone.

  Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

  Usage Guidelines4/5

  Does the description explain when to use this tool, when not to, or what alternatives exist?

  Provides concrete use cases ('which projects were worked on last week or which session was the long one') and clarifies what the tool does not return ('never the text of any message'). While it doesn't explicitly mention when to use sibling tools instead, the guidance is sufficient for typical use.

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

• tool_usageA
  4.3/5.0
  Behavior4/5

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

  Annotations already declare readOnlyHint=true, and the description goes further by specifying return details: tool names and counts, ordering, and the guarantee that tool arguments are never included. It does not contradict annotations and adds privacy-relevant behavioral context beyond the structured fields.

  Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

  Conciseness5/5

  Is the description appropriately sized, front-loaded, and free of redundancy?

  Three sentences, all substantive: first sentence states the aggregation and ordering, second gives the usage scenario, third explains the output and a privacy boundary. No filler or repetition.

  Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

  Completeness5/5

  Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

  With no output schema, the description appropriately discloses the return shape (tool names and counts, no arguments), ordering, and the type of questions it answers. For a simple aggregation tool with well-described optional filters and read-only semantics, this is sufficient to select and invoke correctly.

  Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

  Parameters3/5

  Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

  Schema description coverage is 100%, with each parameter (since, until, project) clearly documented in the schema. The description only refers generically to 'filters' and adds no new parameter-level information, so it meets the baseline of 3 without surpassing it.

  Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

  Purpose5/5

  Does the description clearly state what the tool does and how it differs from similar tools?

  The description clearly identifies the action (count), the resource (Claude Code tool calls across sessions), the output ordering (most used first), and the specific filtering context. The examples of tools and the intent (working habits) distinguish it from sibling tools that list sessions or provide session-level stats.

  Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

  Usage Guidelines4/5

  Does the description explain when to use this tool, when not to, or what alternatives exist?

  The description explicitly states the intended use case: answering questions about working habits, with a concrete example (reading versus editing). It does not, however, mention when not to use it or point to list_sessions/session_stats as alternatives, so it stops short of explicit exclusion guidance.

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

• session_statsA
  4.5/5.0
  Behavior4/5

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

  Annotations already declare readOnlyHint=true, so the read-only nature is covered. The description adds valuable context that it returns counts only and never message text, clarifying privacy and data handling beyond the annotations. 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.

  Conciseness5/5

  Is the description appropriately sized, front-loaded, and free of redundancy?

  Two concise sentences pack all essential information: content of the return value, source for the parameter, and an explicit exclusion. There is no wasteful or repetitive text.

  Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

  Completeness5/5

  Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

  For a simple one-parameter tool with no output schema, the description fully enumerates the return fields (duration, turns, prompts, token usage, etc.) and behavior. It is complete given the tool's complexity.

  Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

  Parameters4/5

  Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

  Schema coverage is 100% and the schema already explains session_id as a transcript filename without .jsonl. The description adds 'Take the id from list_sessions', which is extra guidance on how to obtain the correct value, raising it above the baseline of 3.

  Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

  Purpose5/5

  Does the description clearly state what the tool does and how it differs from similar tools?

  The description uses a specific verb ('Read') and identifies a unique resource ('one session') with a detailed list of what counts are included. It clearly distinguishes itself from list_sessions (which lists sessions) and tool_usage (broader usage stats).

  Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

  Usage Guidelines4/5

  Does the description explain when to use this tool, when not to, or what alternatives exist?

  It instructs the agent to take the id from list_sessions, giving a direct prerequisite workflow. It also sets an explicit boundary by stating 'never the text of any message', helping the agent decide when not to use it. It doesn't explicitly name alternative tools for when not to use, but the guidance is clear.

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